You are correct Ray; there are breads that are more disposed to being mean that others (not too many articles in the paper about attacks from poodles). I have heard of dogs "turning" on their owners, etc. (dobermans, chows, etc.) I do think, though, that the biggest problem, by far, is the owner's way of "training" the dog, or lack thereof. The guy who helped us train our Dane specializes in Rotties. He had one (who has since died of old age) who was the biggest baby you ever met, unless you were up to no good! I also thing that a lot of it is how we as people perceive the actions of a dog incorrectly. This one is hard to explain, but I think a lot of times people mistake an "attack" for a reaction that the dog clearly broadcasts, or just does (for lack of better way of explaining it).
A prime example of the latter: a mom and her then 6 month old girl (or younger) went into the neighbors fenced and gated backyard to give their dog a "treat". I can't remember the bread, but it was a larger bread like a Rottie, Dobbie, Shepherd, etc. Anyway, the mom decided to give the baby the "treat" to give to the dog. Well, the "treat" was a raw steak and needless to say the dog swiped at the steak with his paw to knock it loose to eat it. In the process of swipping at the meat, he hit the child in the face. Long story short, the neighbors had to put their "dangerous" dog down because of the stupidity of that mom! (man that ticks me off every time I think about it - it happened many years ago)