I worked in the PetSmart grooming Salon in Concord New Hampshire, and witnessed DAILY the mishandling of dogs and cats.
Dogs that where "trouble" where routinely choked, yanked around, and pinned (this was usually in the back room where they were being dryed.) muzzles were put on too tight. Terrifed dogs were force dried, and held down with muzzles on.
Breathing impared dogs (shi-tzus, bulldogs, pugs) where put under cage dryers, when it is against policy.
Dogs that refused to enter the large metal drying cages where shoved, choked and slammed into them.
One dog, a basset hound seriously ripped a nail.
Cuts and razor burn were common.. the smaller ones not even being MENTIONED to the owners, who, after being smiled at by the groomer, figured their "little Monkey" had a great time.
I tried during my time there, to come between MANY a stressed out groomer and terrified dog.
When I complained the managers found "reasons" to write me up. I wound up quitting in disgust after making a complaint to the VP, and hearing nothing back.
I now work in a private grooming facility that does not REQUIRE dogs to be done in an hour.