This morning around 9 AM CST there was a database error that ended up causing API slowness for 3-4 minutes, which could have manifested itself on your end as timeouts or spam getting through.
Although the downtime was short it did alert us to a weakness in our system we’ll address so this won’t happen again.
Our last major downtime was in September 2007, one thousand and twenty eight days ago. These things usually happen in threes but hopefully we can head off the next two.
Akismet 
Confirming that this blog experienced downtime such as you describe at the time indicated.
So is this what has caused all the spam to get through? I have had alot of spam in the past few days. it is actually really ridiculous. Thanks for the post!