indestructible oil pump shaft....WHY?

[PROFESSOR FATE]

To tell me that I should use a good shaft rather than an old used stocker is good advice, I suppose, but not exactly what I was looking for. I pretty much dismiss the idea that the old stock shafts fatigue. The only reason I have ever replaced one is because the ends that engage the pump and distributor had worn enough that the darn thing started sticking in the distributor, when I tried to remove it. I can't quite imagine $5000 damage resulting from a broken shaft, unless I pay no attention to my oil pressure gauge or am a blithering idiot. Let's ignore that last possibility/probability or we'll never resolve this. I guess what I'm looking for is real possible failure modes, in other words your horror stories. Ones where at the end you can say "Boy, I'm sure glad that I had that unbreakable pump shaft." or "Wow, if that stock shaft hadn't broken, it would have cost me a fortune."

Several of your responses have been just that. Thanks. The oil pump appears to be the most likely problem cause at the moment. If the pump seizes and the shaft doesn't twist, the gears may well experience several times their normal loads. The most likely weak link will become the roll pin. If that shears off, the distributor gear will turn on the distributor shaft, probably stopping the engine. But, how much damage is done? Has anyone suffered this kind of failure?