Just so you guys know, the rider in the picture had a mechanical issue earlyer befor this happened ... not sure if he had the wheel swaped or just looked at but from what i have herd the wheel fell out of the dropouts or pulled out and thats when the frame broke, probably due to the quick realeas not being tight enough
I was behind him on the first lap. Whenever he got on the power the wheel would jump to the drive side for a second and then back to its normal spot again. I thought he had a buckle in his Zipp but when he pedalled easy or coasted it was dead straight.I also noticed his gears jumped around at one stage.
I moved up and told him I thought his wheel axle was broken, as it certainly wasn't he QR. After that I stayed ahead of him as there was something seriously wrong with his bike and I didn't want to be behind it.
Obviously issues were there before the failure, but he kept riding anyway. OK, so it was a race, but you certainly can't say the rider was blameless in the severity of the failure.
Did the mechanical cause the failure, or was it a symptom? Who knows, but without more details or further inspection you cannot say this is a "frame failure", just as I cannot say it was rider error/poor build.