We're getting hit by a new kind of spam where (I think) human paid spammers bomb forums in real-time to promote events currently happening or about to happen. It can still be effective since if it takes us a few hours before we visit the site and clean it up then it can still get search traffic.
I've cleaned up about 200 threads today, which was the worst one to date. I'll be talking to
Tom about what we can do to prevent it happening again, we've got some ideas.