A lot of the blogs I read use Haloscan for their comments. Many of them are reporting problems with Haloscan in the last 24 hours or so.
Haloscan Fix it guide
Bloggers, go into Beta features in Haloscan and in the middle of the column it says Spam filters. Just say "no" and your comments will come back up. Hat tip Jane for the info.
I'm not a Haloscan user, so this doesn't affect me at all, but I know a lot of bloggers are, so I hope this workaround helps you out.