20k users can vote to delete answers with a score of -1 or lower (at any time, I believe), but the voting lacks a check to see if the answer is an accepted answer. IIRC, accepted answers have to be unaccepted before being deleted, even by mods, so such a delete vote should be disallowed completely.
Since the first one was Jeff's post, I commented on it, but that didn't draw much attention, so I'm posting this. Of course this isn't a huge bug, but it should be fixed eventually.
(Admittedly, I'm very curious to see if 3 delete votes would actually delete the answer and break things horribly. I suspect at least the former would happen.)