Wired reports that Hackers Run Wild and Free on AOL.
"A third hacker, using the name hakrobatik, confirmed the mumbling method.
'I kept calling and pretending I just had jaw surgery and mumbling gibberish," hakrobatik said. "At first I had no info except the screen name, then I called and got the first name and last name by saying, 'Could you repeat what I just said?' Then each time that I got information I called back making the real information understandable, and everything else I just mumbled.'"
I suspect this tactic is so remarkably effective because of the way it plays to AOL's corporate culture. (I've seen design reviews and product direction given with almost exactly the same level of attention.)