Grumpy I can agree with you that people don' always knows what a dog is trying to communicate and in some breeds they may growl and not mean an attack. I've never owned those breeds. But I have seen plenty of dogs(various breeds) get mean and snappy when allowed to play tug of war. It escalates quickly and maybe the dog thinks its a game in the beginning but, it comes to be a contest of strength. Alot of dogs get very heated up over games like that - I consider it teasing. They can get so carried away that they snap or bite without thinking.