David,

The only fan I ever had shed blades was a early Ramtec, and there was an obvious flaw (air bubble visible at the break point) in the molding at the base of one of the blades.
In my experience JMP's quality control was always second to none.
Is it possible that the 3 small screws that hold the rotor hub together were not tightened properly or vibrated loose?
I was always told to use a liberal dose of loctite on those screws to keep them from vibrating loose, and even with loctite I did find one that had come loose on occassion.