Originally Posted by
chaadster
Oh, I have...20 years ago. I ride and race with a lot of people, hang out at a bike shop, and I just don't see it happening normally. Sometimes a noob will build a wheel and mess it up, or try to true one and cause failures of spokes, and even sometimes grossly inelegant riders will break one slamming through potholes, but I think that spoke breakage is pretty uncommon nowadays.
So yes, it happens, but *nobody* has spokes break regularly on multiple wheels on multiple bikes in the same bousehold between different riders like this without doing something wacky to cause it. No way.
Of course there is always a reason why it happens. It is just that the reasons are fairly common occurrences. In addition to all the reasons you mentioned, here is another one: Back in the early '90s I obtained a bunch of "house brand", stainless, aero spokes from Performance. They were wide blades with a pure S-bend at the hub end instead of the usual J-bend + bead end. That way you could attach the spoke to the hub without having to thread it all the way through from the nipple end, which was impossible due to the width of the blade. They were very good looking and inexpensive, but were not worth a crap. Check that...they were worth a crap. They broke constantly. I don't know what Asian source they came from exactly, but I suspect Pillar. In any case, they had to be replaced on the rear wheel after a few months, but I rode with them on the front wheel for years. That was just one of many possible reasons for spoke breakage. Maybe Giant is using inferior spokes.
Interesting what you say about "20 years ago" when straight gauge spokes were more the norm. We now recognize that butted and especially extremely butted spokes are more durable. So it is not surprising the that incidence of broken spokes in quality wheels is declining as the use of highly butted spokes like Revolutions, Lasers, and CX-Rays increases.