An old thread here. As someone that worked for the largest USA campy distributor in the early 80's, we saw many broken cranks not only at the spider, but pedal eye and cracks along the BB tapers. It did happen and since you have to rack up enough cycles of the stressed part, I suppose you wouldn't see as many at retail simply because you have far fewer really high mileage customers. As a west coast gathering point for returns, it was a pretty broad sample size. In addition to the high mileage riders, there are the destructo riders. As anyone that has worked in a bike shop can attest to, there are simply some people that break things on a regular basis. Nice to have for product testing, but hell as a customer.
Bryant Bainbridge
Portland Orygun