On Jan 17th at 20:52 UTC there was a network outage that caused the Akismet.com DNS servers to be unavailable for 12 minutes. The problem has since been fixed, and everything is back to normal now.
This means that for some blogs, there was a brief window where the Akismet API servers were unavailable. If you’re running version 2.5 or later of the Akismet plugin, any spam or comments during that window were held in the moderation queue, then re-checked a few minutes later.
We apologise for the inconvenience. If you’re running WordPress 3.0+ and haven’t already upgraded to version 2.5 of the Akismet plugin, we’d like to remind you to update, since the new plugin includes features specifically designed to recover from a situation where your blog can’t reach the Akismet API servers.
If you’re ever in doubt, you can see independent third-party availability monitoring of the Akismet API servers here.