Nut backed off ball caused accident

Ouch! Good thing no one was injured. I have been towing things for 30 years for tens of thousands of miles and never heard of this happening. I have never had a ball nut be even slightly loose and I used to tighten them with channel locks so I am quite sure it was not over 100 lbs torque. I would guess that for those towing bumper pulls it might be something to check at rest/gas stops as I would think it would take a substantial amount of time for a nut to shake its way loose through all those threads.

I also agree that a cotter pin or lock-tite would completely prevent this from happening.