They're going to try. Australia, already with tough restrictions on cigarette advertising in meatspace, has decided Teh Internets are making young'ns smoke. And censorship will fix that! Oh, my yes, it will. Riiiiiight.
Just how old are these vulnerable youngsters, such easy prey for the merchants of death, the demographic with the greatest proportion of smokers? A mere 24 to 29 years of age. You know, what most people throughout history and across the globe know as "adults." Yeah, they still do think they'll live forever at that age, but they outgrow it -- and, funny thing, the smokers start to quit as the realization dawns.
Most of the Western nations have gone from having a majority of smokers to a shrinking minority and it's getting down to a hard core who like the short-term effects* and either don't care about the long-term ones or are willing to accept the trade-off. Keeping them from seeing ads and putting Scary Pictures on cigarette packs isn't going to change their behavior, no matter how virtuous it makes Nanny feel.
* Inhaled nicotine does wonderful things for my ability to concentrate, YMMV; I was also coughing up yeeech every morning and getting winded on a flight of stairs. So I quit, a long time ago. It wasn't easy. But I don't go around feeling superior because I quit or insisting everyone else ought to.
T. R. MCELROY'S STREAMLINED TELEGRAPH KEYS
9 months ago