There is a difference between a therapy dog and a service dog. Trent, in the video, is a therapy dog. It is up to the handler to control a therapy dog. I could never have let a pet do this in pet therapy in the nursing home where I did pet therapy. BUT those people didn't bond with the dogs and other pets the way this boy has done. Trent and this boy have known each other for a long time; I think it said 2 years. And I'm not sure it IS his head hitting the floor -- you can hear him chuckle right after the noise of him rolling backwards. Mostly, to me, it looks like a boy and "his" dog goofing around.

In general, I'd say the handler was wrong in letting that happen while the camera was rolling.