Apple just announced at WWDC 2012 that Facebook will be deeply integrated into iOS 6 including single sign-on for apps, quick sharing from Notifications, Siri integration, better contact syncing, sharing buttons in the iTunes and App Stores, and a public API.
This stunningly comprehensive integration could see Apple and Facebook teaming up to fight off Google Android and launch more products together.
Full Story: Apple Gives Facebook Deep Integration Into iOS 6 With Siri, Sharing, App Store, API