Apparently there are a myriad roofing defects - something about not enough vent boxes on the roof. He says that made them hotter, which made them break more. Also, he says that when they laid our shingles they put them straight down onto the plywood without the tar paper (or whatever the black lining thing is called).
It'll be interesting to see if the next roofers say the same thing.
The insurance guy comes to see the roof on Saturday. More on this story as it develops.