It seems one of them is the US Department of Treasury, a part of which happens to be the U.S. Secret Service.
If this rumour is true, it points to the not altogether surprising suggestion that parts of the U.S. Government are just as tired of spam as the rest of us. And that they are willing to place their servers in the path of the flood of DDOS attack data that normally accompanies a prominent stand against spam.
Whether a server with those connections will be attacked in the same way as a small privately owned server remains to be seen. µ