any damage at all. Could be that whoever installed the plugs gapped it down too far and then opened up the gap, stressing the metal where it broke off. Then, if it had some stress fractures, the many temperature cycles from everyday use just took its toll and it finally gave up the ghost. I see that it is the proper plug for your car, so I doubt that anything could have physically broke it off unless you had some pieces of piston ring floating around in there or something. But, with 150 psi compression, that's not likely. Just a possibilty. Anyone else?
