A guy popped a front tire on alloy clinchers, and took himself down hard on a descent on a group ride last year. It looked pretty nasty, bent his front wheel up too. I was in front of him of course, but I heard he was riding the brakes like an old lady. I've found on descents it's better to go faster on the edge of control, then to ride brakes, and potentially kill yourself. It was also like a 100deg day when that happened as well.