I heard that the in game friend list is going that way too.
What if you fall out of favour with someone on your friends list, because they actually turn out to be a douche. It could get real ugly.
I have two big issues with this. The nick you use online is an extension of yourself. It's your online persona to deny a person that is pretty sucky. The other issue is obvious griefing on Facebook, MySpace and of course, for the real psychos, RL.
This will go down exactly like the Left For Dead 2 Steam boycott, the bitching about Modern Warfare 2 being dumbed down, draconian DRM issues, etc. There will be lots of noise and whining like stuck pigs and people people will go out and buy the games in record numbers anyway.
Gamers are spineless toadies. The next hit of their particular crack will override any issues they have.