I'm running Version 2.5.6 of Akismet.
Suddenly several of my sites are generating "Comment Moderation" emails for all of them. Previously, I think the local Akismet flags suspected comment spam and then phones home to verify them. Suspect comments (obvious spams) are now sitting for hours with the "Awaiting spam check" flag.
The "Pending" comments no longer have a "History" option to see attempts to check the flagged message.
The core of the problems is that all these pending messages are sitting long enough for WordPress to mail them. Previously messages that went through akismet where labeled spam and only a few stragglers would generate an email.
I have been through customer support with my host, and they say there is nothing stoping traffic to and from akismet's servers on their end.
I am using my wordpress.com Akismet key on several wordpress installs and it validates happily, although it takes 10 seconds or more to load the Akismet configuration screen. The pricing is just way off the charts compared to what I charge to host the sites... like 1:1. I wonder if this is related to Akismet somehow throttling traffic from (over)users of free keys? or free key traffic from outside wordpress.com?