The Freakonomics blog has some interesting points about how to best change behavior. Specifically they point out that trying to get kids to stop doing something by making them think all their peers are doing it (read: all drug commercials) are exactly the wrong approach. As they explain in the post:
These commercials implicitly suggest that most of your peers are going to be using drugs and that you have to gird yourself to be above their influence. They are too close to the signs in the Petrified Forest. Instead of saying “Don’t do what most kids your age do,” they might say “Do what most kids your age do: just say no.”
Huh. Very interesting.