I'm a trainer. I've been biten by three dogs 2 German Shepards and a mini-dachshund as the bites from the Shepards hurt very badly and left some good marks the mini-doxie was the only one to break the skin. In my years of experience the small breeds are more likely to bite, reason being that most owners treat a small dog way differently than a large (you know like a baby). The large dogs that tend to bite are the ones left outside in the back yard all the time. So you see it ALL comes down to the owners the dogs just do as they are told or in most cases they the act because they have not been trained at all.