Does this happen often? Until yesterday I'd never heard of such a thing happening until I saw it first hand. I was canyoneering with a group down one of the canyons in Red Rock and one of the guys in our group degloved his thumb. He was coming over a lip into a free hanging rap and flipped backwards and at the same time his thumb got pinched between the rope and the rock and the skin came right off. It was pretty gruesome. It's really weird to hear about the Yosemite incident right after.