As we all know, teenagers will mimic anything that they see in the movies according to the scientific principle of "monkey see, monkey do." That's why, for instance, you saw so many teenagers transforming themselves into autobots last summer. But should any cinematic depiction of smoking automatically earn a movie an R rating
Well, I'm not sure "teenagers will mimic anything that they see" is accurate. But I'd agree that depicting heros and other 'cool' smoking can and likely does has at least some effect.
To me, applying an "R" rating for praising or showing "unhealthy habits" isn't completely out of the question, but its a bit of a slippery slope. Yes, I think children shouldn't be allowed constant exposure to the glamorization of smoking, but where might this stop? Eating Red meat? Not flossing after meals? Ever see the movie "Demolition Man"? Now, this may also be a slippery slope (in the other direction), but the proposal equates to state legislating of healthy habits; which I'm always a wee bit leery of. There's also the none-too-insignificant point that for many youngsters, all an "R" rating does do is motivate them to want to see it more.
All in all, I'd say "No" - probably an ineffective idea wrought from a good motive. Good sentiment, just likely an iffy way of execution.