Anyway, it sounds like this poor guy got too close to the edge of the face (which is smooth from an ice age glacier - sheer drop of 2,000 ft) and started slipping until he went off. You an see from the pics its bald granite - nothing to hold onto if the incline gets too steep.
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/08/24/BAC01KRB3S.DTL
Here's a link with a good shot of the face and the sheer 2,000 ft drop:
http://www.public-domain-photos.com/travel/yosemite/half-dome-free-stock-photo-4.htm
Another view of the cable route:
http://i52.tinypic.com/34sjqkj.jpg
I had one terrifying moment while hiking in Yosemite near a drop that high by Yosemite Falls. A friend and I got off the marked trail and too close to the edge. I think that's why reading something like this affects me the way it does. Absolutely gives me chills. Anyway, its a beautiful place unlike any other and I highly recommend going there if you can (just be careful!).
