All of us are bound to the grave. A dog may die of other causes, not just cancer. Its also not true that dogs will eventually get cancer if they say unspayed or un-neutered. Experts say that there is only a higher percentage, its not really a certainty. Taking away someone or somethings "gift" is cruel and inhumane. I don't think anyone of us will like to get his "things" cut off, disabled, or removed. Same with dogs. If they could only talk do you think they would agree to have their "things" taken away from them? We could regulate our dogs behaviour if we really don't want to mate. We could fence our yard, we could make a wide open kennel for them, and much, much more. If people does not have enough time to watch over their dogs, I don't think our poor mutts should suffer for it. They are their owners responsiblity after all.