There are now 800 million monthly active users on Facebook, according to Facebook's own statistics. More than 350 million of those people access Facebook through their mobile devices, nearly 44% of its total active user base. In terms of traffic, 33% of Facebook traffic comes from mobile devices - according to data revealed by Mary Meeker in her Web 2.0 Summit presentation this month.

Make no mistake, Facebook is getting serious about mobile. October 2011 was a big month for Facebook's mobile initiatives, with a new iPad app, an updated iPhone app and a revamped mobile browser site that closely mimics the functionality of its iOS apps. It also offers mobile versions for Android, Blackberry and other platforms. But Facebook is just getting started, there's a lot of upside to come.

That 350 million figure for active mobile users will likely increase rapidly, now that Facebook has released new versions of its mobile site and iOS apps.

Also consider that Twitter's mobile traffic represents 55% of its total traffic. While Facebook's comparable figure is only 33%, research company Sandvine reports that 19.3% of all peak mobile traffic in North America (measured in bytes) comes from Facebook. Given Twitter's ratio and the traffic Facebook already drives on mobile, it's a good bet that Facebook will get over the 50% mobile traffic ratio by early 2012.


Source: Mary Meeker

For a more granular look at how the number of mobile users is growing in Facebook, the blog Inside Mobile Apps created this chart using data up till the end of March 2011. At that point, the ratio of mobile users to total users was about 38%. Now, just six months later, it's 44%.

Data released by comScore last week put Facebook's U.S. mobile audience at 57 million users in August, up 50 percent from the previous year. As a comparison, comScore stated that Twitter's U.S. mobile audience in August was 13.4 million people, up 75 percent year over year. Again: now that Facebook has improved and optimized its mobile apps and sites, it's probable that Facebook's mobile growth will look as impressive as Twitter's by this time next year.


Source: comScore

Finally, according to new data from mobile data management startup Onavo, 90% of iPhone owners use Facebook over mobile networks. In terms of traffic, Onavo estimates that Facebook usage accounts for 10% of all mobile data consumed by iPhone users.

All of these statistics show that Facebook already has a huge footprint in mobile traffic. However with a renewed focus on its mobile platform this month, that will most likely ramp up even more.

We are now well into the post-PC era and the largest social website on the planet is making all the right moves to take advantage of this trend.