Looking over your shoulder is not as bad as texting, but nevertheless, both are bad. A moment over your shoulder may not matter much if you're driving in the suburbs or country. But try doing that in downtown LA, where the car in front of you can slam on his brakes at any moment, and you'll realize that fractions of seconds matter. You should try blind spot mirrors. No matter how good you are now, you'll become a better driver with them.
