Gosh, these are Horror stories.
It makes me so angry and sad that anything like this would happen at the groomers. People intrust their beloved pets to the groomers, and they screw up badly. That is not right at all IMO.
This is the very reason that I have chosen to learn how to groom myself on my Suzi. If I mess up, which I more then likely will while learning, at least I know that Suzi is not being hurt or traumatised by anybody. Poor dogs can't tell us about their experiences with other people.
It is heartbreaking. Petsmart and Petco groomers suck.