We have rented a bouncy castle for our somewhat annual block party. I'd guesstimate that out of the 6 or so times that we (as a neighborhood) have done this, there has been one injury that the parents deemed severe enough that they called an ambulance to come take the kid to the ER on a back board. I had to move the cones out of the street to let the ambulance pass.
He ended up being ok, and the kids (my kids) absolutely love the thing. But they are fairly dangerous, and no adults ever supervise what's going on in there. Freaking mosh pit.
