A site like that will be filled with trolls and noobs asking questions like. How to hack my GF's FB account?
You'd think so at first. But then think about how FB works, those people who spam your wall with stupid shit? you unfriend them. (unless you really like them lol)
So when people starting posting stupid crap, and skiddie BS, then real hackers would just unfriend them. Pretty soon theyd be posting only to their own walls, and if you make your profile set to private (maybe make that the default for everyone?) then they wouldn't be able to even see your stuff, or post on it, etc.