I'm against it.
I don't believe anyone should be able to delete their account.
Not only would that make hijacking accounts more of a potential concern, I don't see a good enough reason for it.
Wiping the slate clean, so to speak, so that they can come back here and pretend to be 'new' is not a good enough reason.
Also, if anyone has such an issue that they feel the need to have their account/entire post history deleted for personal reasons (got their feelings hurt etc), then they probably shouldn't have been posting here in the first place.