I have read many things about dog walkers, and I often see many advertisements for them. I view them with mixed emotions.
On the one hand, they can be a valuable resource for the busy person. They will take your dogs and walk them daily for a fee. This may offer an outlet for extra energy as well as bathroom breaks to your dog. They will also likely have other dogs with them which may offer your dog some socialization on leash that it may otherwise be lacking.
On the other hand (I feel like Tevye from Fiddler On the Roof!), most dog walkers aren't trained in any formal program, they may not have the ability or resources to work with behavioural problems, and may not be bondable. There is no guarantee that your dog will be safe in the hands of a Dog Walker, and if your dog has a bad experience you may be in for more than you bargained for. What is your Dog Walker training your dog?
What do you think? Are dog walkers worth the gamble? Would you take the risk not knowing the other dogs that person is walking at the same time?
Personally, I wouldn't use one for fear that something may happen. (I'm a control freak, have you figured that out yet?) I find that long hikes on weekends (4+ hours or more - less in winter) will sufficiently tire most dogs out and regular walks/play time through the week uses energy and prevents boredom. I like to spend time with my dogs as I find it calming. Even taking your dog outside for some good one on one ball/retrieve time.
(Not to mention the question of, why would you have a dog if you don't want to spend time with it? Why not get a cat??)