Only 2 in ten years. The first was when I was fairly new to clipless, at a little uphill intersection with a light. Since then, I have avoided this spot! (8 years ago?). The second was because some idiot on a group ride stopped short in front of me, when a driver was waving us through a crowded country fair area on Cape Cod. I was only going about 5 mph, but I wasn't expecting her to stop and I just touched her wheel and I couldn't unclip. The first one trashed my bars, but not me.