I am seeing errors in the WP admin like: "2 comment(s) could not be processed by Defensio." And when I hit the Process Now button, it just sits there forever spinning its wheels.
I can ping api.defensio.com so I don't know what's up. (Oddly, though, http://www.defensio.com doesn't respond to pings or traceroute.)
Apparently some information on the Defensio forums indicates the service has been down for a day or so now. They say it should be back up, but if you're also seeing this message, you know it isn't.