Four or five years ago, I was at a high school basketball team taking photos for our sports magazine - not the normal HS basketball game, it was televised on ESPN due in part to the presence of LeBron James.
I used to be in the habit of keep one camera on a strap around my neck and one on a strap slung around my shoulder. The camera on my shoulder would essentially be free when I was using it because the strap would fall down.
When I needed the second camera, I would basically drop the camera around my neck and let the strap hold it. It was second nature.
At this game, during halftime, I was taking a photo of Sonny Vaccaro, adidas basketball guru. For whatever reason, my brain was of the opinion that I was using the camera strapped around my neck....
So I let go of it - knew in an instant that a Canon DSLR and an L lens was now heading towards a hardwood floor.
Memory card flew out, screen broke, lens mount damaged, etc.
Thankfully, I was standing on a sideline section of the court and instead of wood, it was some sort of synthetic surface with some give to it. The repairs cost me $400, but it could have been worse and I'll never forget the sickening feeling of letting the camera go.