It should also be pointed out that peer pressure is a two way street. This thread is full of peer pressure not to smoke or to quit smoking. If I were to quit smoking because someone else asked or demanded me to, than I would be giving in to peer pressure. I didnt start that way and I don't plan to quit that way either.
Anyway I think peer pressure is usually a cop-out. No one can make anyone esle do anything except maybe by threat of force. People who smoke ( or drink, or eat cake, or play video games) and blame peer pressure for thier habits show a lack of personal responsibility for thier decisions and consequent actions.