I think it has its place, allowing you to reconnect with people you've lost touch with. What I don't get the the people that post everything they do by mobile phone.
Opened a can of olives, yum. or Just turned on the TV. Stuff like that. I just don't have the ego to assume anyone would be interested in each and everything I do during the day.
I do think that it may hinder us from having a real relationship with friends. I can't see it as enhancing the social experience--I think it dilutes it, giving us the false impression we have friends and are interacting when really we aren't.
good question - what's your take on it?