I haven't broken one, I've bent an F16 mast from a diamond wire failure though. It happened right at the bottom mark. We both hopped on the wire, sheeted hard, then POP. Immediately off the trapeze and back on the boat. So I'm almost certain it would've folded if we had been going down wind, or had not immediately gotten of the wire.
The Goodall wing mast that is on the Viper, and Falcon F16 is really soft. Which is perfectly fine and awesome if you use it correctly. But when someone turns the corner, the mast is rotated back, and the downhaul is on, with crew on the wire, its f-ing freaky looking.

I've seen a C2 mast do some really scary stuff when the other Karl and I were reaching hard to the finish at Steeplechase the second day with the kite up, double trapped and I failed to release the mast rotation. It was ugly. To be fair, it was kite up, kite down, kite up, kite down, kite up, kite down, trying to hold an angle. I'm scrawny, easily winded, and forgetful.