Muppets.

Spam. The site was drowning in it. Not one spam EVER got published - the filters were far too good for that - but the spam volume was so high that the filtering process itself became a problem.

Not to mention it being a waste of time spending hours per day dealing with the delete button.

Ugh, hugs and sympathies

The reason the site went down for a few weeks (and the reason that I turned off all the commenting) was that the spam-comment volume had jumped up to 40,000+ spams per minute.

The site was drowning, and the server administrators were giving me the evil eye.