I have a ball obsessed dog. Cooper eats with it next to him, sleeps with it and carries it around all day. I've gone through periods where I've taken it away from him for weeks at a time and he plays with other toys. As soon as i reintroduce his ball he's back to his obsessive behavior. I've struggled with whether or not to give in to him but he loves it so much that I feel guilty taking it away. I've found that ignoring him when he's barking for me to throw it and playing with my other dog seems to help him get more involved with something else.
I can't use it for training. He's so obsessed with it that he can't pay attention to what I am trying to teach him