Facebook is getting more and more users via its various mobile apps for iOS, Android, Windows Phone and others. However, the mobile versions have been free of the "sponsored stories", otherwise known as ads, in the News Feed section of Facebook. Those kinds of ads have only shown up on the PC and Mac web site.
That will reportedly change very soon, according to an article on the Financial Times web site. The article, which cites unnamed sources, claims that the mobile users of Facebook will begin to see the sponsored stories in their news feed within a matter of weeks.
It certainly makes sense for Facebook to start getting some kind of revenue from mobile users, especially as the company has just filed for its public stock offering. If it can gain revenue via such news feed-based ads from their many mobile users, they can also expand their revenue stream, which is already generating over $3 billion a year.
Facebook began launching sponsored stories in the News Feed for its PC users earlier in 2012. There's no way to block such ads from the news feed and its likely that there won't be such an option for any of Facebook's many mobile app users.