I ban for 404. I hate going through all the trouble of doing reviews only to have the site go 404.
I do realize that webmasters make mistakes and delete stuff that should not have been deleted, I've done it myself, so I'll almost always remove them from my ban list once they take care of the problem. At least if it seems like it was an honest mistake and not something like that asshole from a few weeks ago that did it to all their domains and you could see that they were just cheating.
