At the anon panel, one of the panelists mentioned an interesting spam control method. Having a text entry box invisible to the users labeled "e-mail". A spam bot would see it when scanning the site and fill it out, so any posts that enter text in that box are marked as spam. Not really sure how you would go about making the invisible text entry box, but it's something to think about! But you programer types probably already know about this method I guess.