DoS attack on one of their customers by part of 4chan. AT&T block 4chan. DoS ends. AT&T unblock 4chan.
Someone DoS attacks an AT&T customer. Said person spoofs it so AT&T think it’s coming from 4chan. AT&T block 4chan. Someone with slightly more intelligence at AT&T notices what happened, and yells at everyone until they unblock 4chan.
Blocking 4chan…lol. I dislike /b/tards as much as the next sane person, but like PZ said, gotta respect the terrible might of /b/
UPDATE: Indeed, teh lolz http://www.wired.com/threatlevel/2009/07/4chan/