Shimano Dura Ace 7800 cranksets? I've recently heard stories from two attorneys in different parts of the country that these expensive "hollowtech" cranks may be prone to crank arm failure. I wish to emphasize that to the best of my knowledge there has been no product recall announced, nor am I aware of an serious injury being linked to crank arm failure. Still. In one incident, a bicyclist was pedaling uphill when his Shimano Dura Ace 7800 crank arm "suddenly snapped, throwing him to the ground." In another incident a cycling physician saw his crank brake while riding with it after only three years of use.
Fracture of a crank arm while under stress could certainly result in serious injury. A brief search for more information online uncovered other anecdotes of crank failure. However, it is not at all clear how widespread this problem is.