Because this has happened before. Not just once, either. Facebook's history mirrors that of other imperialist states—frequent periods of radical expansion, followed by intense conflict, grudging acceptance, and then full-throated proletarian enthusiasm.Manjoo, the Slate tech dude, is right. We have been through this before and we will go through it again, kind of like Lost or Battlestar Galatica. Except no smoke monsters or angels, just hackers. And facebook as reached a critical mass, switching to an alternative is unlikely but not impossible.
The real answer is to rely on the advice from Professor Mad-Eye Moody, may he rest in pieces:
The good news, as I said before, is that it is easier to keep an eye (magical or otherwise) on this via facebook friends and twitter buddies who will disseminate the flaws and fixes.