I had my baby groomed at PETsmart for awhile and the groomer was AMAZING, however, she told me the FIRST time before she ever touched my dog that "yorkies are very difficult and often need to be sedated when they are groomed"... I think this is something they are told in training and because of that yorkies freak them out.
She ended up having no issues with my baby and did a wonderful job with him... however she ended up leaving. I used someone new once and she was very upset that I didnt want him shaved, obviously because it is easier, I sat outside the window like a hawk because I felt like I couldnt trust her and wanted to be ready to jump the second I saw the clipper go near his coat. That was no good for him, so I ended up just finding a new groomer. I find Petsmart to be very hit or miss.