Facebook has updated the Facebook SDK 3.1 for iOS, adding the ability to integrate Facebook in iOS 6 as well as other new features. Apple has added several new native features in iOS 6 including Auth dialog and view controller (share dialog). The Facebook SDK supports the use of these APIs.
It's a little bit creepy, but it's also a little bit genius. Singles for Foursquare builds a dating and messaging service on top of the location-sharing application. The result is a mashup that could match up hip iPhone-using, Foursquare-playing, same-bar-going early adopters.