DAU as a percentage of MAU is an important metric to judge “stickiness.” If the company were gaining millions of new users but not maintaining a steady DAU over MAU, it would suggest those users were not finding reasons to return as frequently. In Facebook’s case, the ratio of monthly users returning daily has increased from 44 percent to 57 percent since June 2009. This supports the idea that the social network not only grew in volume but became more engaging. In its IPO prospectus, the company attributes much of this growth to mobile usage.

DAU over MAU grew at its fastest rate between June 30 and Dec. 31, 2009, as smartphone growth took off in the U.S. and Europe. Apple released the iPhone 3GS and Palm released the Pre in June 2009. Motorola introduced the first Droid in October of that year. As millions of consumers purchased smartphones and added Facebook apps, daily engagement accelerated. That period saw faster DAU growth in the U.S. and Europe than it did in Asia and the rest of the world.

The DAU/MAU ratio is not increasing as drastically as it had been, but it continues to grow. DAU as a percentage of MAU increased from 54 percent in December 2010 to 57 percent in December 2011. We can expect this number to keep improving as more users connect to Facebook through mobile apps. Another factor that could encourage more users to engage daily is Open Graph. As more apps and websites integrate Facebook, the social network can increase daily active users without those users visiting the site directly.

It’s unclear how high the percentage will go, but at some point, DAU over MAU will hit a threshold. Investors should keep an eye on this metric to gauge how well Facebook is growing and maintaining interest among its new and existing users.

People who have already added the Comments Box to their website will find that it is now automatically optimized for mobile. The plugin recognizes when a user is on a mobile device and ignores the width parameter so that comments are displayed at 100 percent. Developers can turn this behavior off by setting the mobile parameter to false and control the width manually. Documentation details are available from Facebook’s developer site.

Previously, websites that integrate Facebook Comments had to resize the box for mobile browsers, but there was not a dedicated mobile version of the plugin. This makes implementation easier for developers, and for users the feature seems to load more quickly.

The social network is strongly promoting its comments plugin as a way for media sites and blogs to improve engagement and reduce spam. We use Facebook Comments on InsideFacebook.com and have written about how the feature can sort comments by relevance and affect a site’s Google search rankings.

Image credit: Facebook + Media

As Facebook is likely to introduce Sponsored Stories into the mobile stream early this year, we expect it to continue to bring mobile page functionality up to par with that on the website. We discovered Facebook testing a recommendations section on the mobile touch site earlier today. Mobile pages, though, still lack the option for page owners to customize a landing tab. This would be an important feature if pages gain the ability to run mobile ad campaigns.

However, as more users access the social network through their phones, Facebook’s product designers have to decide which features to add to mobile without making the experience too complicated.

The addition of filters on mobile pages is unobtrusive and they function easily. Users can filter posts by tapping “All” or the name of the page just above the wall. It appears the default view on mobile is the same as it is for the website. Page owners can set the default by going to “Edit Page,” “Manage Permissions,” then “Wall Tab Shows” on Facebook.com. Admins cannot edit their pages from the mobile site or apps.

In May, users gained the option to read and write recommendations for locations and any page with an address listed on Facebook. Bringing the feature to mobile devices has been an obvious next step so users can learn what their friends and others think of places nearby.

For now, users can access recommendations from m.facebook.com on touch devices, not the native apps. Users can search for a page by name or browse “Nearby.” At the top of the mobile page is a “More” option, which includes “Recommendation” in a drop-down menu. From there, users can write a recommendation (and adjust their privacy settings for the post) or read reviews from friends and the general public. As on the web, the default view is recommendations from friends.

Recommendations are only enabled for pages that are associated with a location. Any fan page can gain this status by adding an address to its info section, though it is likely Facebook will one day expand recommendations to all pages, including consumer goods, websites and other services.

When recommendations become available in Facebook’s mobile apps, stores and restaurants may start including “Recommend us on Facebook” calls to action at their locations, just as they encourage visitors to review them on Yelp. When users write on a page wall, that post can get quickly buried by more recent posts. Recommendations, however, are displayed separately and can be highly influential to a person’s friends and other users. They also generate a News Feed story which includes a link for a person’s friends to also write a recommendation.

During the holidays the social network’s apps climbed to the top of the iOS and Android charts, with both Facebook’s standalone Facebook Messenger app and mobile app seeing noticeable spikes in downloads after Christmas according to AppData. The apps are currently the #1 and #9 most popular free iPhone apps.

The story is similar on Android, and as of today, Facebook Messenger and Facebook for Android are the #1 and #2 most popular free Android apps.

The numbers are a nice cap to the year for Facebook, which focused heavily on its mobile strategy in 2011. Mobile companies accounted for more than half of the acquisitions Facebook made this year and one of those companies — Beluga, which the network bought in March — developed the social network’s standalone messenger app.

Facebook also finished the year with more mobile users than ever, according to Enders Analysis analyst Benedict Evans, who estimates that the social network’s mobile apps now have more than 300 million MAU. Unsurprisingly, the iOS and Android versions of Facebook’s apps account for the lion’s share of its mobile userbase. Approximately 117 million people log in to Facebook’s mobile app every month from an iOS device and 87.8 million from an Android device. In addition, almost half of all Android and iOS device owners have installed Facebook’s mobile apps.

This story originally appeared on our sister site, Inside Mobile Apps.

In September, Facebook announced it had 350 million monthly active users accessing its services through mobile devices. This was 100 million more than it had said were active on mobile in March. As the social network introduced a mobile app platform to third-party developers in October, we expect it to continue to build its expertise in this area next year.

Rel8tion – January

The stealth hyper-local mobile advertising startup was acquired and brought into Facebook’s Seattle office. The social network hasn’t yet announced plans to bring ads to its mobile experience, but there have been reports that this could happen before Spring 2012.

Pursuit – February

Facebook hired two of the three founders of this professional network startup that helps employers promote job openings by using their employees’ social networks. So far we haven’t seen Facebook add more professional networking tools, though there are several third-party job apps growing on the platform.

Beluga – March

Five months after Facebook acquired this group messaging startup, the social network released a standalone messaging app that has been one of iOS’ top free apps since it debuted. The success of Messenger could encourage Facebook to develop more standalone apps, for instance one for quick photo-sharing.

Snaptu – March

After partnering with the Israeli startup earlier in the year to bring the app to 2,500 different kinds of mobile devices, Facebook brought the team on presumably to continue to build smartphone-like experiences on basic feature phones.

Recrec – April

This was a talent acquisition, rather than a a traditional acquisition, but most of the founding team of Dogpatch Labs-incubated startup Recrec joined Facebook. Recrec had been developing technology that automatically converted images into HTML and CSS.

Daytum – April

When Facebook hired the two founders of this New York-based startup, we suggested the new employees could help the social network track and visualize activity such as photo uploads, checkins or wall posts. As it turns out, the new monthly and yearly summary boxes on Timeline look a lot like Daytum, which lets people manually enter data such as trips to the gym, films watched or food consumed.

Sofa – June

The social network acquired this Dutch development and design startup for its talent, not its software products, which include Kaleidoscope for tracking differences in text and images, Versions for code version control, and ecommerce platform Enstore.

Digital Staircase – November

Facebook fueled speculation about a possible standalone photo-sharing app when it acquired Digital Staircase, maker of a handful of photo and video editing apps, including MovieCam.

MailRank – November

The social network picked up two former directors of engineering of Second Life-maker Linden Lab in a talent acquisition of MailRank this fall. It did not provide details about what the pair would be working on.

WhoGlue – November

Unlike others, this acquisition was not for talent. Facebook bought Baltimore-based social networking software firm WhoGlue Inc, a company it had sued for patent infringement two years ago. The renamed WhoGlue LLC continues to develop private social networks for its clients.

Gowalla – December

Most recently, Facebook brought Austin-based Gowalla co-founders and other key team members to Palo Alto to work on product and engineering. The social network did not acquire Gowalla technology. The location-based service will be closing sometime in January, according to a blog post by co-founder Josh Williams.

Image credit: Gowalla

January

Redesigned Profiles
Facebook started the year with a new look for profile pages. With Timeline on everyone’s minds now, it can be easy to forget that 12 months ago the social network had redesigned profiles to include more photos and information at a glance, eliminating the horizontal tab structure that had been in place since 2008.

All-in-One Messaging
Users began to get access to the new Messages product, which groups all direct messages between users whether they are viewing a conversation from the inbox, chat window or mobile.

Sponsored Stories
In an effort to make advertising more relevant by including social context, Facebook introduced Sponsored Stories that allow advertisers to pay to promote activity on the site, such as likes or check-ins. The company added more Sponsored Story types in April and June.

Memorable Status Updates
Perhaps hinting at the nostalgia-inducing Timeline to come later in the year, Facebook began displaying users’ status updates and stories from the past.

Secure Browsing
Facebook started giving users the option of accessing Facebook over an encrypted connection and encouraged developers to obtain a Secure Sockets Layer certificate to make their iframe apps accessible to users with secure browsing enabled. Since then, the company has prompted users to switch to HTTPS and made SSL certificates mandatory for all developers.

February

Page Redesign
Page owners got a number of new features to help them manage their communities. These included activity notifications, “Use Facebook as a Page,” and a spam filter for comments. Fan pages were also designed to look more like the new user profiles and place pages, which displayed applications vertically on the left hand side rather than in tabs across the top. Advertisers also gained the option of driving ads to any landing tab, not just the default.

Improved Like Button 
Clicking the Like Button began sharing full-sized stories in the News Feed rather than the one-line Recent Activity stories it previously generated. This along with the Send button that came in April have replaced the Share button, which Facebook no longer supports.

Real-Time Commenting
Facebook made commenting more like chat by removing the “Post” button and instead publishing comments after a user hits “enter” on the keyboard. Since this leads to more accidental comments, Facebook later began giving users a 12-second window to edit their comment.

March

Questions
After a Q&A product similar to Quora never made it out of beta in 2010, Facebook relaunched Questions as a poll feature aimed at helping users get recommendations from their friends. Pages began using the feature to engage their fans with questions that had a more viral effect than plain-text posts.

Deals Subscription Service
Facebook seemed to be taking on Groupon when it began a new pre-paid deals service for users in select cities, but it discontinued the test in August.

April

Updated Groups
Ahead of the rumored Google+ launch, Facebook made improvements to its Groups product aimed at helping people share with subsets of their friends. Most notably, group admins gained the ability to approve people before they are added to the group. Users could now also upload photo albums or ask Questions within groups.

Send Button
The Send button was introduced as a way for people to share articles and third-party websites with groups of friends, whereas the Like button posts to all a users’ friends.

May

New Ad Analytics
Facebook made several changes to its advertising analytics dashboard to focus on performance indicators such as Page Likes, app installs and social reach, rather than older online advertising metrics such as CPM.

Recommend This Place
The social network implemented a recommendation box on place pages (and fan pages that included an address) so that users can share their opinions about a location or a business.

Tag Pages in Photos
Users and pages gained the ability to tag other pages in photos they share on the site. This increases the reach of any given photo and builds additional connections between users and pages.

June

Happening Now: Prelude to Ticker
Facebook began testing a “Happening Now” module on the right hand side of the page. This later became the Ticker, which shows more recent activity from your friends, including comments, page likes and now Open Graph activity like listening to a song in Spotify.

July

Mandatory Credits
All developers on the Facebook platform became required to use Credits as the sole payment option for their social games. The company had announced a July 1 deadline at the beginning of the year and then added additional payment options and feedback channels for developers over the next few months to support the transition.

Video Calling and Group Chat
Teaming up with Skype, Facebook integrated video calling into its chat product. The social network also expanded group chat to friends who were not already in designated groups. Users can now add any friend to a chat conversation.

August

Revised Privacy Controls
The company simplified its privacy settings page and moved controls to the profile editor and news feed publisher. Users also gained the ability to approve tags in photos, check-ins and statuses.

Canvas App Page Changes

Facebook made several changes to the Canvas Page, bookmarking and games stories in the news feed in order to improve game discovery, retention and user experience. The redesign added a real-time activity ticker dedicated to stories about a user’s friends engaging with games.

Expanded Ads API
Facebook brought its ad API out of private beta and began allowing more developers to build tools and services that programmatically create, buy and manage Facebook ad campaigns.

Standalone Messenger App
Moving away from its all-in-one mobile application strategy, Facebook released Messenger as a separate app to rival texting and group chat alternatives.

New Locations App for Pages
Some corporations gained access to a beta product that allows them to designate multiple locations under a parent page and include a store finder on the page.

September

Timeline
At F8, Facebook unveiled a new version of user profiles that organizes stories in a timeline format, giving users the option to add life events to any point in their personal history.

Open Graph Application Platform
Along with Timeline, the company announced a new way to connect people and objects beyond the Like button. Developers will be able to make apps that let users share what they are reading, watching, listening to, cooking and more. Along with this comes “frictionless sharing” and additional avenues for app discovery.

Reconfigured News Feed
To accommodate this new type of Open Graph app, Facebook redesigned the home page to include News Feed and Ticker.

Subscribe
Facebook introduced a new one-way follow dynamic with its Subscribe button. Users can subscribe to the public updates of anyone who allows subscribers. This gives the social network a way to compete with Twitter and Google+.

Smart Lists
The social network introduced Smart Lists to automatically group users’ friends by location, workplace and school. As users become comfortable with Facebook grouping friends automatically, we could see Facebook’s algorithms creating more nuanced lists that compete with Google’s Circles feature.

October

Mobile Platform
After much speculation, the company unveiled a way to help mobile developers market their native and HTML5-based apps through its platform. Developers can now take advantage of bookmarks, requests and the news feed in the same way that Facebook canvas developers do.

Talking About This
Facebook added a new public metric to pages called “Talking About This.” This metric encourages pages to think about engagement, not just accumulating Likes.

iPad Application
Facebook released its official iPad app after months of leaks and rumors about its development.

November

Sponsored Stories in Ticker
The social network began showing Sponsored Story ads in the Ticker, signaling more lines being blurred between paid and organic content in the future. The company later told us Sponsored Story ads will be shown within the News Feed starting in 2012.

December

Timeline Goes Live
Facebook began its global release of the Timeline profile developers had gotten a preview of at F8. Timeline is still opt-in for users until sometime in early 2012. The company also debuted Timeline on mobile devices for the first time.

Coupon Test
We discovered Facebook testing a new coupon post feature for pages that could have big implications for next year. Pages that are part of this beta can offer discounts and promote them with Sponsored Stories.

Private Message Test
We have also seen the social network testing a way for users to privately message page owners. This, too, could have a big impact for people using Facebook for business in 2012.

The mobile news feed is a bold step as it will likely increase engagement for cross-platform games that can be accessed via Facebook’s HTML5-based mobile platform. The stories will appear to both gamers and non-gamers, depending on how frequently the games are played by their friends. Developers can track referrals to games from stories that appear in mobile news feed by looking for ref param “feed_gameplay”. Facebook also recently announced plans to introduce Sponsored Stories to the news feed in 2012. We expect those to end up in the mobile feed soon, too.

The updated game categories addresses the rise of new genres on Facebook in the last year. The all-new categories include “Casino,” “Family,” “Sports,” “Strategy,” and “Word.” Old categories “Role-playing” and “Virtual world” now appear as “Adventure,” and “Simulation,” respectively. This brings Facebook’s total count of game categories to 12.

Lastly, Facebook has combined the the apps and games dashboards into a single dashboard called “Apps and Games.” Facebook explains on its blog that this is intended to “grow the apps and games ecosystem by creating a single place where users can discover and re-engage with [their] apps.” Friend invites appear at the top of the dashboard with a “top apps” section below that showcases what apps a user’s friends are accessing the most.

Facebook has also updated the number of app bookmarks from four to six. The social network reports that an early result of this small change is a 20% increase in referrals from canvas bookmarks to games. Additionally, bookmark counters on the home page now clear automatically when clicked by the user, similar to how notifications behave. Lastly, the platform now features a Games Tutorial for developers just starting out on Facebook.

Facebook has long wanted to make its Events product a tool for users to organize casual get-togethers not just parties or big events. Still, users are unlikely to use the feature for more spontaneous plans unless Facebook introduces a way to create events from mobile that can compete with the efficiency of group text messaging.

In the mock-up Facebook provided to illustrate Sponsored Stories in the News Feed, we noticed a design and name change for Events. Instead of “Create an Event” being on the right hand side of the home page squashed between Ticker and ads, there is a “Make Plans” option in the publisher at the top of the page. Last month Facebook made two other semantic changes within Events — using “Join” instead of “RSVP” and “Going” instead of “Attending.” This less formal language could lead more people to use Facebook Events for everyday plans.

Whenever Facebook has made changes to Events, designers have emphasized the product’s potential for spur of the moment gatherings. The first time event creation was added to the publisher, an official blog post suggested it was a way “to plan a more spontaneous get-together.” When Facebook added an Events box to the home page, the blog post mentioned “casual get-togethers,” “an impromptu day trip” and “last-minute plans.”

The website no longer features a way to create events from the publisher or directly from the home page. Users are also unable to create events from the iPhone or Android apps. The mobile touch site includes the capability, but the design is not optimal since the many of the buttons are too small.

To really get users making plans with Facebook Events, the company would have to develop an even easier flow and bring it to the native apps. Events could be an appropriate addition to the standalone Messenger app, which has made one-to-one and group messaging faster than in the main Facebook app. Some mobile apps, like Holler and Hurricane Party, aim to give people ways to create events on the fly, but without integrating Facebook’s social graph, they are of little use.

Facebook wants to position itself as a platform providing the tools for users to share social data that can be accessed by any developer to create new applications, but the company doesn’t shy away from encroaching on someone else’s territory. Developers operate in fear that the social network may eventually release a competing product, crushing smaller competition with its massive userbase. Checkin services, photo sharing apps and group messaging platforms have all faced this challenge, and it is unclear whether Facebook will wait for the pain points of organizing impromptu events to be solved by a third-party developer using the Events API or integrate this into the Facebook product itself.

These ads would be particularly effective for mobile games and apps since they would drive directly to a point of conversion. Other companies would more likely find value in mobile Sponsored Stories if Facebook expanded the coupon feature we discovered it was testing last week. This would give brands a way to present consumers with a stronger call to action than liking a page.

Overall, putting Sponsored Stories in the News Feed would give Facebook a way to serve targeted ads to the 350 million users currently accessing the platform through mobile devices without compromising the user experience. This would be an important move for the company should it decide to file for an IPO in the spring, as it would indicate an opportunity to increase revenue.

How Sponsored Stories Would Benefit Games and Apps

When someone uses an app or plays a game on Facebook at least twice or for at least 10 minutes in the last month, it becomes eligible to be a Sponsored Story promoted to a person’s friends, according to advertising materials from Facebook. Developers can pay to display an ad that combines this activity with a thumbnail image and a call to action to play the game. If this type of ad were brought into the mobile News Feed, it would be a huge opportunity for mobile developers. Facebook recently began offering distribution channels for mobile apps, including support for sending users to native iOS apps or directly to a download page within the App Store.

Formerly, it didn’t make much sense for mobile apps to advertise on Facebook because pushing users from the web to a phone is a large barrier to entry and makes it difficult for advertisers to track conversions. But bringing Facebook’s demographic and interest targeting to a mobile environment through Sponsored Stories could be a game changer if click-throughs and conversions can compete with other mobile ad networks.

Sponsored Coupon Stories on the Way?

Last week we spotted Facebook testing a way for pages to post coupons and promote them with premium ads. Clicking to get the coupon sends users an email voucher and generates a story on their Timeline. If Facebook expanded Sponsored Stories to include this type of activity, companies could pay to promote the fact that a user got a coupon. This could work just as well on mobile. Further, it gives brands more control over what they present to consumers since traditional Sponsored Stories do not allow for customized messages.

Without this type of ad, Sponsored Stories on mobile could be a weak offering for pages, since the only possible call to action would be to like a page. Sponsored Stories on the web can direct users to custom tabs that provide greater incentive for users to connect with the brand. Tabs are not accessible on mobile, which could mean lower conversion rates for gaining new fans.

Zuckerberg: ‘Ads Should Be Content’

Facebook has always been careful about how and where it implements ads. Facebook CEO Mark Zuckerberg’s disinclination for advertising is well known, but Sponsored Stories seem to be something he can get behind.

“The basic idea is that ads should be content,” Zuckerberg says in “The Facebook Effect,” which was released before Sponsored Stories were introduced. “They need to be essentially just organic information that people are producing on the site.”

Since Sponsored Stories are derived from users’ friends’ activity, companies cannot simply pay their way into the News Feed unless their content is engaging. Facebook has successfully brought Sponsored Stories into the App Ticker and News Feed Ticker streams without major complaints. Inserting these ads into the mobile News Feed is not likely to result in the type of backlash that could come if Facebook inserted traditional banner or interstitial ads.

And by expanding its ad inventory to include mobile in this way, the company could significantly increase revenue and give credence to the $100 billion valuation some have suggested.