Definately a resounding YES to Pet Sitters Insurance. I was, for many years, the only insurance adjuster in the country that investigated pet sitting claims. These claims ranged anywhere from suicidal dogs to dognapping and everything in between. In this world you have to cover yourself. Make sure you know the laws of pet sitters in your area and don't take dogs to the dog park. Dog parks are accidents waiting to happen not only for the dogs but for the people as well. People are very attached to their pets as they are a part of the family unit, however, there are a few 'wacos' out there that will torment you if something happens to their pet while under your control. The laws are changing in the courts as to how much a pets worth is monetarily. Pet Sitters Insurance is not expensive and it has great coverages. Even if you are a responsible pet sitter, something is always going to happen and a vet bill will be the result. Remember, dogs are pack animals and if you have more than one dog with you and they have never met, you might be in for a terrible experience.
I hope I haven't scared you as you need not be scared on starting this venture. Feel free to ask me any questions regarding pet sitting and insurance. Best of luck!