...said the Symantec manager. "We've moved away from traditional, individual spammers, to loosely tied groups of spamsenders, malware coders, and people selling access to botnets," Sjostedt said. The largest botnet sending spam originated...
http://news.zdnet.com/2100-1009_22-187107.html
...proprietary anti-spam sytems (for those who prefer such things to FOSS). Plus RBLs and other methods of detecting spam-senders before their spew enters the network in the first place. Drako says that he has a Removal Request page and staff...
http://www.linux.com/feature/155880