I've always believed that it is the owner who causes any breed to be vicious and never really considered it's reputation as a reason not to get a pit bull. I probably wouldn't get one just because I prefer other breeds, but the reputation of the dog has never given me concern. I've encountered plenty of sweet pit bulls and I've never encountered a mean one. I often wonder if the fact that people are uneasy around them adds a little gasoline to the fire and prompts them to be on edge themselves.
That said, about 3-4 months ago I saw a little boy who was mauled by a pit bull and the dog focused on his face. I saw them bring him into the hospital and got a really good look at the damage. His cheek was torn open in such a way that I was almost positive he would have a scar like Heath Ledger on the one side of his face. It was sort of lifted up a bit and the term I heard used was "degloved". A portion of his upper lip was entirely gone, from the center of his upper lip spanning about 2cm to the side. Basically a 1cm X 2cm piece of lip just not there. They brought this part of his lip in after picking it up off the ground but apparently it was too damaged to be reattached. He had smaller cuts above and below his eyes and he's probably fortunate that he didn't lose one.
I still believe that it's more so the owner than anything that drives pit attacks, but what if you just happen to get a bad egg? Could happen with any breed I suppose but I think the potential for damage with pits far exceeds the potential in other breeds. I'm about as certain as I can be that I would never have a pit that would attack someone as a result of my ownership, but I just cannot imagine how horrible I would feel if I just got a bad egg from the bunch and the dog really went after someone the way this pit did to this little boy.