As with any physically demanding activity, doing it wrong or without strecthing properly will most definitely hurt you in the long run. I've been bedridden for a whole day for forgetting to stretch after boxing the day before. It's really just a matter of being careful and taking care of your body.
I love quadrobics because walking on all fours feels very natural and freeing for me. However, yes, it can be dangerous if you're not careful. Once I was doing quads for half a day without good preparation and the next day I felt like my body was falling apart. Don't do like me! I'm just dumb.
I think it's fine. AND it's really really fun!
Okay, this is all well and good, but it concerns me that I can't seem to find a proper stretching tutorial that reaches all the muscle groups affected by quadrobics. I'd make one myself if I knew anything about how sports affects the body, but unfortunately I don't. I think it's important that there be something like that out there so that people don't jack themselves up even more with a bad stretching routine. Do any of you know of one that's actually good?