A while back. Haz went off on a tear about something, and instead of acknowledging him, the rest of the posters in the thread instead just started very obviously ignoring him and talking about the best roller coasters in the country or something instead. It turns out that Haz doesn't respond well to being ignored, and after throwing a tantrum (which everyone continued to ignore because it was getting hilarious), he started spamming the thread with hundreds of posts, each containing dozens of huge images, giant blocks of text from Dawkins or Hitchins or something, and just generally trying to break the board.
But it turns out you can just delete posts, so no harm done. I wasn't even going to ban him until he started trying to break other threads on the board as well. There was a man who did not deal well with being ignored.
EDIT: I think it might have been waterslides rather than roller coasters.