Never had a brake failure, but I have caused the drum to heat up to the point that it was smoking. This was descending Deer Creek which is longer and steeper than the Westlake side of the hill that the Tour of California will be using on its final stage (May 23, 2010 for those of you who want to watch it). I am sure that the Tour riders (Lance Armstrong, etc.) will be using their brakes much less than I do, but our team/bike weight is probably close to two and a half times theirs and our brakes are not that different. Oh, and I don't pretend that I can descend as well as Lance - I go a lot slower.
It only takes one time for a heat caused blow out, brake failure or fade to get your attention. Had a friend go down last weekend on a sharp corner on a descent while riding a 300k. Broke his hip, surgery, four titanium pins with a potential for a future hip replacement.
Brakes are good. Using them is good. Having brakes when you need them - priceless.
Ride Safe.