Answer: This (hat tip to ASPCA). Many people don't know what a pit bull looks like, and lots of breeds look similar. Even my wife, an avid reader of Dog Fancy, went through more than a third of the photos on that Web page before she picked the American pit bull terrier. You have to really know your stuff to tell them apart. Do your neighbors or local police have that knowledge? If they do not, your perfectly harmless and legal pup could be taken away in a case of mistaken identity.
Our experience with pit bulls is mixed. The pit bull at the end of the block, Snowman, acts aggressively, and our dogs don't like him. His owner knows this, however, so he keeps Snowman behind a tall fence and doesn't walk him around other dogs. On the other hand, we have taken care of two young pit bulls found on the street for a couple days each. The only problem we had was when our dog -- sweet, docile Teddy -- attacked the first one. Teddy was fighting for a treat that the pit bull had dropped. After Teddy knocked her on her back, she bit his leg. At first I was mad at the pit bull, but clearly it was just a scared dog defending herself. We found a home for the second pit bull, and her owners love her; she's a good dog.
That is another big problem with breed bans. Pit bulls are not inherently aggressive and dangerous, nor are rottweilers (another breed often singled out). On the other hand, under the right (or should I say wrong?) circumstances, beloved breeds can be violent and unpredictable. Granted, a bichon frise isn't going to maul a six-year-old, but a poorly bred or trained German shepherd might. Even a labrador retriever will bite if you back it into a corner or taunt it.
Dog attacks are tragic, but the breed bans being considered in many states and local jurisdictions are not the answer. Responsible ownership, proper breeding, good training, and common sense behavior by people around dogs would go a long way toward solving aggressive dog problems.