How are you supposed to escape from harassment on Facebook? A person who is stalking you or otherwise bothering you can be blocked, but can then set up another account and harass you from there. Do you just have to block every new person from sending you messages? Are you supposed to abandon your old profile and start a new one for greater privacy? Somehow I doubt Facebook wants us to throw away profiles that are heavily-laden with juicy marketing data only to start again and lock everyone out.
You need a way to disconnect a certain identity front - a kind of nickname - from a Facebook account so that nobody looking for that nickname would ever find you. But to make that method effective, the nicknames need to be the only way people interact with Facebook.
Mokalus of Borg
PS - That level of privacy protection will not happen.
PPS - It's too much work for something that Facebook does not value.