Yeah, I have. It's happened to a couple of people I know, plus others I've read online. The two people I know it happened to don't post here, and there wasn't a thread about it. However I can give you the story from my friend, he brought it up the other day actually as it's the acceptance time of the year again. Here's the email he sent me:
" I received the letter from USC around early march saying I had been accepted into the class of 2009, about a month after my interview. I was thrilled, it's a big school (700+students) and I couldn't wait to hit up the beaches of southern cali [he's an out of state applicant]. So the letter was official, had a signature from Pete Vanderveen (the dean) and I couldn't wait. I denied a few acceptances and was on a couple of waiting lists, but USC was my school. So anyway I show up to orientation in August and a secretary notices we have like 5 extra names present (you signed in) than were officially 'accounted for' on the computer. So this immediately sends a shocked secretary to grab to dean and talk to him in his office. Shortly after the 5 "extra" including myself were given a ridiculous "apology". It seemed the computer had mistakenly labelled denied applications as accepted, and letters were printed off and mailed without a confirmation ( double check ). So the bottom line was, we were pissed off and freaking out and the dean said there was nothing he could do and was 'deeply troubled' about the events. I got up and left."
Crazy eh?