Yeah, I've heard that Google is getting worried about being made redundant by the growth of Twitter and FB. Whene something newsworthy happens people go to Twitter of FB to get reaction and news rather than Google - That worries them I suspect
I doubt if any other social network can beat Facebook and Twitter. Google is doing it to makes Facenook's users fewer. And it can reach to this purpose a little. But i am sure Facebook will have much more users.