Originally Posted by Trevtassie

I have, big man here with full touring rig, bike and gear over 110lbs. Going down a very steep mountain sealed road with random patches of gravel that meant you couldn't pulse brake or go fast enough for air flow to be effective. I've also been riding with a dude who had one fail on his MTB, luckily it was the back. Funny thing was he was talking not 5 minutes before about how superior disc brakes are.
Here's the point: discs do have a failure mode to zero or minimal braking from heat build up, in circumstances which can be achieved in the real world. Braking techniques in steep terrain while heavily loaded need to be modified to take this into account. To say otherwise is to deny basic physics. Rim brakes can cause blow outs in extreme circumstances from heat build up but cases of the brake failing to stop are much rarer than with disc brakes.