We were towing a boat from our cabin a while back and all of a sudden the trailer passed us going down a hill. It went off into the trees, about 1/8th mile off the road. It passed through the trees without a scratch!
What happened was the ball had broken off. It wasnt to heavy of a load for the ball or hitch, it just broke. That is why I cringe when I see safety chains wrapped around the ball! (this trailer never was towed further than about a mile, so it had no safety chains).
My uncle one time figured it would be a good idea to haul his 11-1/2 foot camper on his 1/2 ton 73 dodge, and pull a 26 foot boat. Well, the truck had the power, but the right rear axle snapped and the tire passed him on the freeway. surprisingly, nothing got hurt, and the truck came to a controlled stop. that one still baffles me.
Last story, I was given a free trailer one time. It was a triple axle 28' flatbed backhoe trailer. I had to get it right away, because there was another person it was given to also, and I had to beat him. I was told it had a regular ball, so I drove to pick it up, and it was a pintle hitch. So, I took the ball off my reciever, set the pintle on it, and liberally wrapped it with a chain. It made it all the way to my driveway, where the chain broke, the trailer fell and trashed the jack. oh well, it was still free!!!