My husband was helping his sister and nephew get their boat out of the water on a lake.  They were at the city boat launch.  The boat was on the trailer and hooked to the hitch on the Trailblazer.  As my husband was pulling the boat out of the water and up the ramp, the trailer of the boat came off the ball on the truck.  The chains were attached so the boat did not go back into the water but when he stopped the trailer was pulled forward and caused damage to the back of her vehicle.  Now his sister and nephew are saying he was going too fast and that is why it popped off.  I am not sure of the degree of angle at the launch.  The truck does not have 4 wheel drive.  It does have something special to do with the traction (posi-traction?) so he was giving it gas and not moving much so he gave it a little more to get it going.  Another friend, whose husband and father have a lot of experience hauling race cars on trailers, said the reason it came off was either it wasn't hooked securely or the ball is the wrong size.  They said it has nothing to do with how fast he was going or the angle from the ramp to the road.  I am not sure he was even up to the road yet before it popped off.  What is your opinion?  If you go too fast on the incline or at the angle can it pop the hitch off the ball?  He wasn't going that fast as you then pulled out into the street.  We have a medium size camping trailer and my husband also has experience hauling things and is not careless.
Thanks for your opinions.  

Your fried is correct.  More than likely, the ball was the wrong size or the trailer was not latched properly.  The way a trailer hitch is designed, there is a latch that comes underneath the ball securely holding it in place no matter what the angle.  I have a boat myself anf have encountered some pretty steep ramps in my day.  These hitches are designed to work on almost any terrain or at any angle or speed. They all designs have to be approved by the DOT and this is known to be a very reliable design.  Even more so than a boat ramp, they need to hold at high speeds, over speed bumps, around corners, rough terrein, and constant accel/deceleration.  Hopefully this was helpful.  

Definitely either wrong size ball or not latched properly. I would know as I tow my race car trailer all the time. If your husband has experience towing trailers it unlikey his fault its more likely that it was the wrong size ball that his sister and nephew bought