You are perfectly correct that the end temperment isn't set until 2-4 years old. Goliath turned 1 on 11/13/05 so we keep a good eye on everything he does and he gets LOTS of socialization (puppy park several times a week, daily walks in the neighborhood, lots of time with our kids and their friends etc ....) spending as much time as possible with other people/animals. But still I trust his instincts over my own as far as who are "good" people. I believe that dogs (especially any breed that is basically an old fashioned castle guard dog) has the correct sense of who to trust and who not to. The real test is that you will never know you are being protected by a protective dog (as opposed to agressive) until their services are NEEDED, like the breakin incident. You would never have guessed that Goliath had a viscious bone in his body until that moment (except maybe for the stuffed .... then unstuffed toys ..... LOL). The truth of the matter is that there is no such thing as a completly trustable dog (no matter what the breed is) because no matter how we feel about them they are still animals.
BTW - the name was my wife's choice ..... sadly it was one of the conditions of getting a puppy that she got to name him ..... I would have prefered "Fluffy" or "Tiny"
Matthew and Goliath