One of the problems, at least in the states, is that alot of animals get lumped into the "pit bull" group. Half the time when the media reports about a pit bull attacking a human....if you dig into the story a little more, they are not pit bulls. That is not to say pits don't bite people....indeed, it happens. But when the media reports a pit bull mauling, and it turns out to be a completely different breed all together, or a mix, etc....the damage is done. That headline is out there, and you can't take it back with a back page apology. I think that is one issue that gives them bad names...along with massive over-breeding.
@Fairlynew is correct....A LOT of dog bite injuries are from smaller dogs, because they are cute and fluffy, and people feel comfortable getting into the face of a small dog. Hell.....I got bit this weekend by a miniature doberman pinscher with an ego problem!!!