It seems the lesson to learn here is the relative strength of freestanding boulders for rappel anchors, rather than the technique used to lower the patient. How many times have you lassoed a rock and rapped off it with a nonchalant "looks bomber to me" because you want to get out of there? I know I have a few times. Clearly it does pay to minimize the number of lives exposed to risk should it blow though. Very sad.