My older brother has always had Pitbulls for dogs and they all have always been very sweet and have never once bit a person.
Right now my brother has a two year old female pit and He has a 4 year old daughter who plays with the dog, lays her on, jumps around with her, can get right up in her face and the dog has never once done anything aggressive nor has she even gave off a warning like "you better get out of my face!" growl or bark. and he has another kid on the way.
Just like any other type of breed if the dog is not raised right, it will not act right. Any breed can be aggressive not just pits.