I worked at Anheuser-Busch for 8 years and rarely saw any spam get through their filters, but one of the few times it did, it ended up causing chaos (at least for IT).
I worked in a business group with a small handful of programmers, we saw the spam hit our inboxes and just deleted it. One of the guys we worked with though wasn't quite so smart, he hit reply and asked to be removed from the mailing list. Something in the e-mail caused his response to be sent back out to the entire company (to this day not sure if he hit reply all or what if it was something coded in the e-mail). What followed was an almost day-long stream e-mails from various people all across the company. There were some asking to be removed also, others telling people to stop replying and on and on. To the point that if I remember correctly, IT had to shut down everyone's e-mail that night to clean out the Microsoft Exchange servers and remove all trace of that one e-mail.
We got a good laugh and never let the guy who started the whole thing forget it.
