Facebook has been testing a project with select developers that allowed them to pay to put ads in your mobile news feed to advertise their apps. Clicking on the ad would launch the iPhone App Store, or Google Play Store to the advertised app, allowing you to purchase it.
Now, Facebook has opened up this feature to all developers. This allows developers to buy their way into your news feed, regardless if you or your friends like the app or company. From the test group, the developers that used the service saw an increase in click-throughs to their app, so it appears this could be a good move for developers and for Facebook, but not necessarily for us end-users, especially if the ads are intrusive.