I wouldn't say all the time, but they happen frequently enough. From the sounds of it the rider was on an intermediate slope and then somehow slammed into a cache of trees. The main reason I believe this is that someone saw it happen from a lift. Almost every collision death in Colorado has one thing in common. They were on an intermediate run. I am not sure if I can remember a death on a black diamond, and I think the girl who died in the freak accident was on a green. Otherwise, it's the middle of the road runs that are the killers. If you are on a black diamond run or truly riding in the trees, you generally don't pick up enough speed to get killed. Sure you can get jacked up, but the speeds are generally lesser than at what you can cruise on a blue groomer.