Something odd happened. There was a spammer that posted a thread. I deleted the account but left the thread intact. Appropriately, the post showed: Spammer Guest However, today a new member signed up and now the post shows: Username New Member I looked at the database and it seems that the new member was assigned a user_id that's the same as the deleted user. I believe the expected behaviour is that deleted user_ids are skipped when someone new registers. The new member registered via facebook, so maybe the user_id bug only happens with Facebook Connect?