(Why stop at Native Dancer? Heck, let's blame the Darley Arabian. I bet all the horses that break down are descended from him. Definitely his fault.)[/QUOTE]
I think the only sure fire reason for horses being unsound is the all mighty dollar. As the previous poster mentioned, horses in most other sporting arenas that have huge conformation faults are gelded. Owners are being responsible in those instances and not caring how well he may do in said sport and the potential stud fees they could acheive. The dollar could be blamed from trainers to racetracks. Do whatever you have to do to get a horse to a race and keep the racetrack profitable no matter what the cost to the horse is.
(I hope that paragraph makes sense... my sentence structure is a bit off today )