Well, i can give you guys the real cause. In the July edition of Rock and Ice there was a very informative short article on it. The man and his partner had a 200 foot rope, with no middle mark on it. They dealt out half of the rope down the cliff, so that it was touching the ground. They figured they could just throw the other half of the rope down and it would be the right length. It was a very windy day at the coulee, and what they didn't notice was that the wind had actually pulled more of the rope through the chains, leaving just 12 feet at one end. The man began his rappel, but the rope quickly shot through his rappel device. He grabbed the end of the rope before it got out of reach, but slipped within seconds.
Great apologies to you, and kudos to those who tried to help him.