Malcolm Gladwell's 2006 New Yorker article about troublemaking dogs talks about how specific dog breeds are often banned when attack numbers reach a certain point, but that in reality, it's often more the fault of the owner than that of the dog. 
The strongest connection of all, though, is between the trait of dog viciousness and certain kinds of dog owners. In about a quarter of fatal dog-bite cases, the dog owners were previously involved in illegal fighting. The dogs that bite people are, in many cases, socially isolated because their owners are socially isolated, and they are vicious because they have owners who want a vicious dog.

"A fatal dog attack is not just a dog bite by a big or aggressive dog," Lockwood went on. "It is usually a perfect storm of bad human-canine interactions -- the wrong dog, the wrong background, the wrong history in the hands of the wrong person in the wrong environmental situation."
Many locales have mandatory neutering programs for dogs who have a history of attacking.  I think we should extend this practice to their owners.  People who breed and train attack dogs that they themselves can't control should be stripped of the privilege of contributing to the gene pool. #nature