Facebook has proven that they can make money in new areas. They went from 0% of their revenue on mobile a year ago to 30% of their revenue on mobile in Q1 2013. This trend won't be stopping, mostly fueled by mobile app download market. Companies are paying HUGE dollars to get their apps downloaded, but not just by certain people, by highly targeted demographic (eg: Women, 25-40 who live in the mid-west, who also like Oprah). Facebook is the only mobile advertising channel that can provide this level of targeting at a HUGE scale (trillions of pageviews a day).
I work in mobile advertising myself (top 3 network in the world) and EVERYONE is getting their lunch ate by Facebook right now. We're losing money left and right because everyone is moving their spend to Facebook. For example: look at $MM and $VELT, both leaders in mobile advertising, both have had terrible quarters since Facebook got into the mobile advertising game.
Mobile advertising is a HUGE market and is only getting bigger, and Facebook is positioned to be the leader for the next 3-5 years, at least.
As a comparison, $MM did $50M in revenue in Q4 in mobile advertising. $FB did $350M. They're already doing 7x what the leaders in mobile advertising are doing, and they're just getting started.
More people are using Facebook than ever before. Monthly user numbers climbed 23% year-over-year to 1.1 billion, while daily users increased 26% to 665 million.