I had a friend, deteriorate rather quickly his first time up to Horseshoe Meadow. My guess is if he stayed the night he would have had a rescue type of event.
I believe it is rare but I believe it can happen. I've seen people with no history AMS get delirious at 11,000' after a hard day in the mountains. I have problems if I over exert, while taking Diamox. Diamox is not a panacea, it is tool to help those of us who have problems in the mountains. If not used properly or if you do too much, it does not work all that well.
