As an anti-smoker, I have to say I hate anti-smoking comericals. All they do is give it that same "i'm going to live forever" appeal that teenagers are looking for. Most smokers know tabacco companies are evil anyways... I'm not sure what the right way to market the message to teenagers, but it's still certainly an unsolved problem.

You can join a whole bunch of PhD behavioral psychologists in not knowing what the right message is for teenagers!

FWIW, I will say that some of the common wisdom doesn't always hold true. Like "pressuring someone to quit doesn't help". I quit precisely because of a lot of friendly pressure. Emphasis on friendly.