I volunteered at The Evergreen State College Bikeshop for a year, and at least once someone came in with plastic pedals where the CPOS bearings (maybe just metal bushings?) had bound and literally worn through the plastic pedal body, so the rider was stomping on the steel spindle to transmit power, with some plastic bits hanging on.
Come to think of it, the spindles of such pedals might even be pot metal, i.e. melted down Chinese cookpots and Buddha figurines... so the snapping thing might not have been the plastic at all!
Oddly enough, my 30+ yearold Schwinn Sierra mountain bike has what appear to be CPOS pedals, but the ballbearing are actually serviceable. Sigh.