The last two days?
Well, on an image board threads die to make room for new ones, due to disk space and bandwidth being finite. On a message board, well, I'm not convinced either way there about old threads, which I've mentioned before. Regarding Slashdot, the idea is tempting, but apparently flawed, at least as implemented by Slashdot. As they do it, it promotes groupthink and pleasing the majority. If you wanted to explore an interesting side track, you could consider designing a board around a system like, for instance, Amazon uses to find things it thinks you'd enjoy - let users mark things as "liked" or "disliked", and then based on your choices and the choices of others, figure out a weighing that promotes things that are liked by people who have in the past liked the same things as you. This, of course, requires registration (unless someone can think up a clever way around this), and isn't very suitable for this kind of board.
So in summary: Moderators are an unfortunate compromise, because no other model has presented itself. If one was presented, I would be all for it. In the meanwhile, I am of the opinions that moderators should only function as janitors, and clean up after malicious users, but not otherwise get mixed up in the running of the board.