Aren't all of Apple's social graphs tied to an iTunes login? At least they are consolidating them across their own network. But, I guess since I can't FaceTime

Aren't all of Apple's social graphs tied to an iTunes login? At least they are consolidating them across their own network. But, I guess since I can't FaceTime my Game Center friends, that's not very useful... Also, yes, I don't really care if Apple does social as I wouldn't want to invest in another network either. It seems though they are trying at it and failing, rather than just ignoring it.