There was rider out here in WA at Crystal Mountain last season that fell in a tree well and was not found until the summer thaw. They're dangerous. Even in-bounds, they're still there and just as dangerous. The avalung is not a bad idea, but most people would not be wearing that while riding in-bounds, and it's almost always in-bounds that someone falls into a tree well. It was for me, and it was for the poor person that lost his life at Crystal last year. The majority of people just assume that if they are in-bounds, then they are safe.
Do you mean inbounds as in the resort or inbounds of a groomed trail?