An Engadget reader running iPhone OS 4.0 on a jailbroken device found references of Facebook contacts integration into the OS. The references come in the shape of a .plist file called “FacebookContactsConstraints.plist”, but Engadget also reports that Apple may include a larger social network support by integrating services like Twitter. Indeed, it seems like “SocialKitInternal.framework” is mentioned somewhere in the OS, but they’re waiting for proof.

While I think that integrating these services might be a good idea and Engadget believes that Apple is thinking about including a “linked contacts feature”, I have the feeling that this is stuff was originally meant for sharing and suggesting apps to your friends and followers. If Apple really decided to extend the support for social networks, my money says Game Center will be included and Google services (Buzz?) won’t obviously be supported. Sure a Facebook-powered Contacts.app would be great.