I know some will say it is all in how you raise them etc etc but there is a reason why they have all these problems with pits. When I was a kid we got a puppy from the pound and it was boxer/pit. This dog was never mistreated and was always aggressive! We thought it might calm down with age even after taking it to all those puppy training classes that everybody says most dogs need. Needless to say after having the dog a year or so my parents had to put it down after digging out of the back yard and attacking a little kid. Luckily it only bit his shoe and pulled on his pants. When we took it to the vet the last thing it did was growl at the vet. The vet said a lot of the pits are inbred and it causes mental problems with the dogs.
That being said I know not all dogs even pit bulls are like this and I currently have a dog (lab) and I am an animal lover but when people have these dogs they need to be kept secure at all times. Pit bulls are more likely to be aggressive! You can also check actual dog bits and the majority are from pit bulls by far! You are a pit owner so I know you probably know everything I have said already. Just remember don't take roaming pits for granted just because your pits have been well mannered dogs. Many are not like that.

Edit: Also, the people I know who where attacked, one a close friend both thought the dogs where safe and the owners were present at the time and said the dogs where gentle as could be. At no time had the dogs showed aggressive tendencies toward people. Both petted the dogs and for what ever reason the dogs didn't like them and attacked without warning.