Unless it's someone from the old CML crew, which doesn't seem likely (They don't seem to be bragging about it on the forums they currently inhabit), the only possible motivation for a grudge against us is the old SPP/BMG thing. And frankly, I don't think something on this scale is in Joe's ability to do.
We seem to have weathered the storm, by making the entire domain 403 everything for a short time, but we can't be totally sure yet. Things are back up, but the server load does seem unusually high.
I have to wonder who else is sharing this server with us. Perhaps it's not our traffic which did everything in, but rather some new script or feature another site on the server is running, sucking up system resources.