9to5 feels they have a reliable inside on the Facebook integration:
"According to sources familiar with the Facebook integration into iOS 6, the integration will be very similar to Twitter’s integration that launched with iOS 5. The integration’s biggest presence will be in the iOS Photos application. Like you are able to send photos to Twitter from the Photos application, you will be able to post photos to Facebook. A single sign-on section for all Facebook connected applications is present in the iOS 6 system settings application. Like with Twitter, a new “social sheet,” as some people familiar with the matter call it, will appear for an accompanying status message."
"Besides content sharing, Apple is also relying on Facebook for a big new social change for the built-in App Store: a feature called “App Liking.” Discoverability has always been a major downside of the Apple mobile apps market with hundreds-of-thousands of software apps, but Apple will by relying on the world’s largest social network to help fix that problem. Inside individual application pages on the iPad, iPhone, and iPod touch App Store will be a standard Facebook “Like” button. If a user is logged into Facebook via iOS Settings, these app “Likes” will be sent to their Facebook Timelines. Accompanying status messages will also be an option."
I'll be curious to see what permissions users are granting by allowing Facebook access.