Oh, I can go even smaller than either of those breeds, how does Pomeranian hit you, bear in mind, we're talking 3 to 7 pounds of pure fluff:
http://archives.cnn.com/2000/US/10/09/pomeranian.kills.ap/
Okay, had to go to the year 2000 but I don't usually memorize dog bite incidents.
Like I said, ANYTHING that has teeth can bite, and the fact is, theoretically ANY dog can potentially present a danger. All it takes is one incident, it may be the ONLY incident ever in that dog's life, but shit happens unfortunately. What a lot of fuzzy headed people don't grasp is that animals are not people. You cannot expect them to act like people or think like people (you would be astounded at some of the shit I've heard people say about their pets).