There is such a thing as bad publicity, as evidence Sony's recent debacle should be evidence enough. However when you sell a product that is designed to kill, like cigarettes, then what is considered negative becomes vastly skewed from what would be expected from a normal product. Strangely, since Heart Disease is the number one killer of both men and women, that obvious cardio killers are not looked upon in the same villainous light.
It turns out that teens who see the anti-smoking ads are more likely to smoke. Maybe they can see through the haze of BS that comes from ridiculous attempts at using mass media for social engineering. If you want kids to quit smoking come up with a decent transference mechanism. Something that meets all the needs that are currently being fulfilled (or in non-smokers being unfulfilled.) As Personal Philosophers (some call them psychologists) would bring up is the problem with unfulfilled desires and what happens to the beings in which these desire reside.
I think ultimately the smoking numbers went down as people pretended to be oblivious to the idea that smoking was dangerous. Now that the pretend naivete has gone, people have taken the habit back up, and the younger generation is following suit. The best quote is this:
"Even parents who are smokers can make it clear and communicate to their child that they wished they hadn’t started smoking, because the majority of smokers do feel that way."
As if any person exists outside of the social spectrum, as recent studies have shown people are outnumbered by televisions in homes. This means that the average person is bombarded by images and some take them to regret their life and others realise, importantly, that TV is FAKE. Tell your kid not to smoke if you want but remember when they get to be 18 they will do pretty much whatever they want.
Oh and quit with the mass social engineering, people get enough of it in public (and private) school.