one of those kicked my ass when i was younger, i had been riding dirt bikes since i was small, but only been on the 3 wheeler a couple of times
long story short, i went up on two wheels and dirt trail instinct kicked in and i tried to right myself with my right foot, it ran up my leg and tore most of the skin off, tore my knee open on the footpeg, then drug me underneath and hit me in the back of the head, i woke up in the hospital
no permanent damage, but i definitely understand why people say they're dangerous...i was only doing maybe 30mph and a small trench in the pasture that would have been no problem on a bike was what felled me