I did that once, hit a deep pothole, pannier w/ work laptop flew off right in front of a bus but it rolled to the side so the computer survived. Whew. Those panniers I have since relegated. My 10 yr old still uses them to carry board games or nerf weapons over to friends' houses.

I have dropped taillights several times. Sometimes from the mount, other times they just pop open and spew batteries all over the place too.

I've resumed riding my bike that has a computer lately and twice in the last week when I park it in the garage at home the computer is twisted in its mount. Not sure when that's happening, if it's moving the back past my kids' into the garage, or during the agony of climbing the last hill.