Apple needs to stop trying to build it's own separate social graph for each features (Game Center, Find My Friends, Ping, maybe even Facetime) and give Zuckerberg whatever it takes to integrate with Facebook for friend discovery like everyone else is (i.e. Foursquare, Instagram).

I wish I could see what kinds of games my friends are playing, but the mental stress of thinking through who I know has an iPhone, and manually searching for them just makes it not worthwhile.