Mark Sutton killed doing this. He slammed into the side of the mountain at over 100mph.
He was James Bond stand in at the Olympics. Other articles state he was in pieces when they found him.
http://tinyurl.com/pxgwus9
Jeb Corliss, who is from New Mexico, is a world famous wingsuit flyer. He broke both legs clipping a ledge on Table Mountain in South Africa. He uses regular helium balloons suspended at various heights to gauge his clearance at certain places on his flights. A flyer in front of him caused the balloons to drop and the strings got tangled in a bush. They were too low and he hit. Fortunately, there was enough of a drop off on the other side that he could deploy his chute.