This is not really a kitemare but it does highlight a danger that as an intermediate kiter I was unaware of. I was out kiting in the waves at a local spot and having a great time on my twin tip, when whilst accelerating around some white water I put too much pressure on my heel side edge which popped out of the water and left me kind of skipping along the surface with my butt in the water and my board still on my feet out in front of me - a situation which I'm sure almost all kiters have been in plenty of times and that I would have considered to be pretty innocuous. On about the third or fourth skip however, just before I was about to attempt a recovery back onto the board, my right foot slipped out of the footstrap, allowing the board to rotate on the next contact with the water, badly breaking my left ankle (I heard a clear crack), as my left foot was still trapped in its footstrap. Nine months off kiting, and serious disruption to all aspects of normal every day life work etc over that period.
Although it seems pretty obvious to me now, at the time I was totally unaware of the high numbers of ankle injuries that happen due to one foot being stuck in a strap (most commonly from jumping). My IKO instructor never mentioned it, and I'd never been warned about it from more experienced kiters - I guess because it's not actually life threatening.
Since the accident I have discovered that ankle injuries are quite common in kiting so beware getting stuck with one foot in and one foot out.