Facebook will be integrated more with the launch of iOS 6. The Facebook SDK 3.0 Beta for iOS has recently been released for the developers to tinker with. With the SDK, Facebook for iPhone, iPad, and the iPod touch will soon be enhanced for a total social networking experience.
Expect better user session management, Ready-to-Use Native UI Views, Modern Objective-C language features support, and improved Facebook APIs support.
The iOS 6 integeration will allow the phone to automatically use the Facebook Login when needed and when available.
You can download the beta with iOS 6 integration HERE.