I'm not a teenager. or a girl. I'm 10.
So err, if Anonymous were to take down Facebook, that would render them criminals more then when they took down Sony, since Sony bitched, leading to SOPA and PIPA.
Facebook did nothing wrong, it's made for people to talk (Especially teenage girls, seemingly)
And facebook is very huge. Meaning a lot of employees. Taking it down would render all of them jobless.