Who's been following all the footing drama? Between the trial in California on the "sport surface" and Susan Garrett's dog's tumbles at regionals, my own little circle of agility is all abuzz with pronouncements of "I will never trial outdoors", "I will never trial in the rain" and more.
Between those, a person would never be able to trial again. The sport surface was indoors, SG was outdoors... that's pretty much everywhere.
Our local trials are almost all on dirt (indoor arenas), which is varying degrees of good. Depending on how it's prepared, it can be softer or harder, pebbly, etc. Generally, I think it's a pretty safe surface for dogs, though it can be harder for humans to run on. I know people who will pull if they don't like the way the dirt is prepared, but I've never seen the need. We do still have a few that are outside on grass, and the Rose City Classic is run inside on very nice rubber mats.
I'll run on pretty much any surface, and I don't think I've ever scratched a run because of the surface. I've made different decisions based on surface, ie; the RCC used to be held on carpet, and I ran one day of it once (my 2nd actual agility trial, and I'd only entered the one day), and decided that dog shouldn't run on carpet. I went to another trial which was held on carpet a few years later, and didn't enter that dog, but I did run another dog I had, who was slower and more cautious. She did fine.
I've run in the rain, more than once, and it's not been much of a problem for my dogs. I did use to train outside, and we ran in the rain then, so my dogs were used to it. I train in a barn now, so I might be more wary of it. My dogs are fairly sure-footed, though. I've actually seen more trouble with
dry grass, which tends to get really slick, and I'm not sure I'd run on it again.
When I took Tess to World Team Tryouts, which is held on artificial turf, she had some trouble with that surface. We'd practiced on turf before we went, but the turf at Tryouts was harsher, and she managed to tear her stop pads on the practice day. Not badly, but enough to be a bit tender. I know now to toughen my dog's feet if I ever go again. And not play tug on that turf. I did run her anyway, and she did alright, but I think turf is not a great surface for her. Interestingly, when we were at Purina Farms for our Nationals a couple weeks ago, their flooring was turf, and Tess still seemed a bit slippy on it. I was sure that Pirate, who is faster, would struggle, but he actually did great on it. Tess did slow down (because I was slow, not because she was slipping), and then she did alright with it.
My dogs have injured themselves in many dramatic ways, but never a real injury from agility. They've needed a chiropractic adjustment after doing something spectacularly stupid, but that would be the extent of it. I do kind of feel like their potential to get hurt in agility is so much less than what they do to themselves if I don't police them. However, if they were continually stressing themselves the same way in agility, I would choose to retrain, or not run on that surface/equipment/whatever. They're just pretty creative about finding new, rash things to do.