Are Some Shimano Dura Ace 7800 Cranksets Prone To Break?

What's up with 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.