The worst I've seen actually was a near-miss, when the opening keynote speaker didn't show up until the very last second, didn't answer her phone, and left the organizers scrambling to shuffle the schedule around to come up with someone else who could do a credible job of opening keynoter. But she did show up, albeit a bit late, and the show went on. I must live a sheltered life.
Of course I've also heard of horror stories like keynoters dropping dead on the dais; and natural disasters like a twister dropping in on an outdoor exhibition. And, of course, there was 9/11, when meeting planners at the World Trade Center had to shepherd their attendees through the unimaginable and others had to find ways to get their people home. It still hurts my heart to read their stories.
But somehow, no matter what you have to deal with (and check out the "everything-that-can-go-wrong-did" story Mike McAllen tells on Meetings Podcast), you manage to get through it all.
So, what's the worst thing that's happened at one of your meetings? How did you cope with it?