I've handled over 500 used bikes in the past few years. Liability selling used parts & frames has been a concern since most alloys break without warning and steel forks might have cracks that aren't easily found in a quick inspection. I've seen 3 bars that were bent, all at the edge of the stem clamp. I've personally never had a bar break nor have any of my close riding buddies, knock wood! I think that a hard impact like a pothole at 30+ MPH would be a good candidate to break one though, particularly in my gravity challenged physical condition. Lou