I've heard some horror stories so definitely do background checks and ask around. I rarely trust my dogs to anyone else.
Absolutely there are bad dog walkers around too - I see them doing all sorts of unacceptable things, eg, tying dogs with good recall up with ones that have no recall so they cannot run off. I see other dog walkers that [this was before the 6 dogs per walker law was brought in] would open the back of a van door let 20-25 dogs dash out, let them to run around for 10 minutes or so - long enough for them to go toilet, [bear in mind dog walks are always advertised as an hour long] then herd them all back in the van again and if they missed the odd dog well never mind.......... The amount of times other park users have found lost dogs isn't funny and TWICE I have found the SAME DOG lost by the same INCOMPETENT dog walker......grrrrrr.........makes me so angry. I have seen dog walkers leave dogs unattended in their van/car while they go looking for missing dogs. I got totally berated once by another dog walker who parked in the car park on the other side of a very busy road - traffic doing 50 miles an hour, he opened his car door and his dogs jumped out of the car and ran this way and that. At the time I was getting my little pack of dogs who were all on their leads into my car as we had finished our walk. One of his dogs saw us and ran out of the car park and over the road - the traffic was screeching and braking so as to not hit the dog, lucky the dog got to me. The dog walker stood on the other side of the road and took his time getting over to me, I was chatting to the dog and trying to keep him calm, he wasn't within my hand grasp so I didn't try to get him as I didn't want to frighten him into running back over the road again. The dog walker finally got to us and started calling the dog - the dog ignored him and started to play with him - jumping away making play bows so the dog walker turned his back on the dog, and started swearing.........now bear in mind we were to a really busy road, so I took out a treat and lured the dog towards me with it as he got close enough I was able to grab his collar. I said to the dog walker - I got him, do you know instead of being grateful, he started saying I should never have used treats, the dog will never learn to listen, etc, etc...I cannot repeat here what I said back to him.........fine to train the dog his way when it doesn't stand the risk of being run over!
But these are examples of the worst of the worst, you have to remember that very little gets said about good dog walkers - bad dog walkers will always attract attention and then all dog walkers get labelled the same way. Having been in this line of work some time now, I know alot of dog walkers, there are far more good dog walkers than there are bad ones.
Maybe you could ask friends who are pet owners too. Or search on the internet, everything's almost online nowadays. It's better to research than be disappointed at a later time and could result to a damage to your pet.
Stephanie, your experiences of bad dog walkers are really alarming, it just shows how careful you need to be. Thankfully I have only had good experiences with people taking care of and walking my dogs, so I would echo what you say, there are many good and reliable around.