yeah like you said if they want to steal ur car they will
the idea of not letting the car start without the computer was discussed on the nissan silvia forums and it was said that if the thief is really prepared they will have a truck, and after braeking in all they have to do is roll the car on the back of a truck. thats imn the worst situation of course
but like adiryboy said the best thing is probably a good ytfracking alarm so it significantly cuts down the time the thief has the car in their possession