I love clipless fail stories. Mine was back on the MTB doing some urban rock crawling (stair cases etc). I bottomed out the crank and the rest is history. Never had a problem since. Back then it was just SPD MTB system. with the SPD-SL the worst I get is not locking the pedal IN. Pedal Struck my shin hard enough to bruise the bone and cause a hematoma, which is still there (wasn't that long ago, maybe a month). Started heat therapy and the whole calf turned green and purple. It kind of sucked to say the least.