Yeah those can be nasty... whats really wrose is when I read about people who have a rearing horse and quote trian them to do it on command.... Ummm lets see train a bad behavior on comand = rewarding a bad behavior.

Though the other day my trainer was talking about rearing horses and a way to trian them to stop. You load your hand full of eggs and when they rear smash the hand full of eggs between thier ears. Make sure the eggs drip down the horse's head so she thinks he hit his head on something and is bleeding... Sounds like it could work.