Although I grew up with dogs, and like dogs well enough, I haven't had a dog of my own. Every time we have a vote about getting a dog, the cats vote me down so I'll probably never have a dog. When I was working with Blue Buffalo, I came to meet several dogs, and can usually tell whether a dog is going to be mean or not. Usually, the ones who are the most likely to do you harm are the ones who are scared rather than the ones who are mean, and they signal that to you if you're paying attention. In my experience, it seems like the smaller dogs were the most likely to bite, or to threaten to bite, while some of the gentlest dogs were the large breeds. One woman would come into the store with an Irish Wolfhound, I think it was. That dog was huge, yet when it wanted to interact with a smaller dog, it would lie flat on the floor so that it wasn't towering over the other dog, and it was so careful with any other dog that it was playing with.