That's an easy one. For the one millionth time, PIT BULL IS NOT A BREED. Theoretically, 'Pit Bull' encompasses four different breeds: Pit Bull Terrier, American Pit Bull Terrier, Staffordshire Terrier and American Staffordshire Terrier (that's what Pooh is).
In actuality and unfortunately, many dogs that bite people are automatically labelled as Pit Bulls when they are other breeds. If you want to see for yourself I suggest you visit the Find the Pit Bull Game. It may surprise you.
You also have to keep in mind that the idiot press hypes the crap out of fatal dog bites, but they are very, very rare. From 1979-1996 there were an average of 17 per year. If you go take a look at the report from the CDC, you will see that they acknowledge what I said above by putting the 'Pit Bull'in quotes. You may also be surprised to see (look at the chart) that in several of the years other breeds were responsible for more fatal dog bites than the amalgamation of breeds now known as the 'pit bull.'
From personal experience-- I have been in animal rescue for almost twenty years, and I've worked in big city pounds for almost all of that time. Most people are quick to hang a Pit Bull sign around a dog's neck. I've seen it with lab puppies, full grown Shepherd mixes, Saint Bernards and Siberian Huskies. I've even heard veterinarians say 'this dog has Pit in it,' which as a statement is not only ignorant but laughable (this particular dog was clearly a Shepherd/Akita mix).