Some of the dogs in my pack really like retrieving balls, especially from the water. There is nothing more joyful than watching dogs charge in to the waves after a ball and then surf out. I never get tired of watching that.
However some of these dogs that enjoy ball retrieving take it to unhealthy level. The ball becomes their heroin. They cannot function if there is a ball in their vicinity that is not in their mouth or under their control. They jump all over the human trying to throw the ball and get into resource guarding fights with any other dog that comes near their ball.
These dogs will go after that ball until they are literally crippled. They practice no self regulation so it is up to their humans to to regulate them. I have witnessed quite a few dogs injure their legs badly enough to to require surgery from excessive ball play. In hot weather these dogs will go after that ball until they collapse from dehydration. It is completely up to their humans to regulate their behavior.
I understand why dog owners get into the ball retrieving game; it is a quick easy way to exercise your dog without actually taking them for a walk. One of my clients has one of these nut cases. He is 80 something years old and has a young energetic golden retriever. He more or less stands still and throws the ball for her all day everyday. As a result she has become progressively more neurotic and less comfortable hanging around with other dogs and seems to be somewhat confused on hikes without her ball.
In conclusion, my feeling about ball playing is that it should be done in moderation as part of your dog's playtime if he or she enjoys it. Ball playing should not be your dog's only exercise. Regular walks without the ball and socialization with other dogs is also critical to a dog's well-being.