It seems that someday soon, bluetooth phones & PDAs might eliminate the need to store common destinations in the car's navigation system, and just allow you to navigate to entries in your contact list, which would move with you as you move from car to car.
But until that point, an uncomfortable
wealth of information is actually stored in these systems. If someone were to steal my car, they would know where I live and work, where my parents live and where my son goes to college, etc.
This exposure could be eliminated by letting me set a pin or password that would have to be entered before using the navigation system. For simplicity in usage/customer care, a "I don't remember my pin" selection could either be reset at the dealer or wipe the memory and allow the setting of a new pin.