Last week we experienced a comment spam attack from China. I found out that when that happens, Akismet temporarily suspends their API key and stops working. Over 3500 spam comments stacked up in the Pending queue before we blocked a large range of IP addresses from China. Fortunately, Akismet does capture the IP address of the comment submitter, so was easy to identify the IPs of the attackers with a simple MySQL query.
The bad part was that Akismet stopped working an all sites that use that API key, so we had spam comments stacking up on multiple sites.
"It's inexcusable for scientists to torture animals; let them make their experiments on journalists and politicians." -Henrik Ibsen