In most forums (not all), I think it would be useful to have a mechanism that automatically locks threads after a certain amount of time has passed without a reply to the thread (say, six months or a year) in order to prevent someone wandering in through a Google search or something from bumping a thread that has long passed relevancy back to the front page. It is almost universally recognized that just making a new thread instead of bumping a very old one is the better course of action, so why not codify this behavior and prevent necromancy from occurring without moderator approval?