I was whizzing down a Pennine descent this afternoon at about 55 kph. The surface was bumpy, with the odd pothole. It struck me that it was similar to the descent that Contador was doing when he crashed, except that he was supposedly doing 60 kph at the time, and obviously was surrounded by lots of other riders. I toyed with the idea of taking one hand off the bars to see what doing the descent one-handed felt like, but thought better of it. At that moment my front wheel hit a large rut that I hadn't spotted ...
I know those guys are great bike handlers, but sometimes I think that 'familiarity breeds contempt'!
I've seen riders get their jackets caught in the front wheel on descents. I actually think they wouldn't lose much time just stopping and putting on/taking off the jacket safely.
I've even seen riders who had tried to adjust front wheel computer magnets on descents and lopped fingers off!