Facebook has just opened up it's Audience Network to all advertisers & apps. This network is not a separate set of ad inventory from what is displayed in Facebook's own apps, but simply it is an extension of Facebook advertising already across multiple apps.
This is huge news for Facebook as they will allow for growth in their mobile marketing, cashing in big. About 62 percent of Facebook's ad revenue, or a small $1.66 billion, came from mobile last quarter.
Be on the lookout for more targeted ads from Facebook throughout your apps.