I broke an I20 mast at the Nationals at Tybee Island a few years ago. Heavy air. Came around A mark and started moving well but stuffed the bow hard and the mast snapped from the shock load. Main was still sheeted I never blew it. So it can happen.

I've seen a Hobie Tiger mast snap too.

I've personally snapped a Hobie 20 mast in big waves reaching with too much weight on the boat. I'll call that one my fault.

Mike Hill - Snapper of masts.
N20 #1005