I'm in favor of the seatpost clamp theory here, either the clamp was over tightened or the clamping area was very small, possibly a burr on the edge of the clamp caused a stress riser on the rails.

I have seen a very nice looking "Ritchey" seatpost that was a counterfeit item and it was junk. It would not sufficently clamp the saddle rails, the clamp was poorly designed. Fake parts are out there, they look genuine but they are not.

Another thought - does the rider "un-weight" going over bumps ? I hear people saying they want to ride lightweight wheels and other parts "are those wheels OK for a 240 lb rider" ?

My response is that it's all about riding style. Some people are very easy on equipment. Others, not so much

/markp