[spaceribs]

Well it's certainly at the whims of a network-effect, that's part of the reason alcohol prohibition was so insanely ineffective. There was more people who wanted alcohol than the ban could possibly handle.

I'd posit that indoor smoking bans wouldn't have been effective whatsoever if they were implemented in the 1970's rather than the 2000s, just for the simple fact that 40% of the population were smokers compared to around 20% when those bans came into effect. Additionally, the impact to smokers was that you needed to go outside to smoke, which is a pretty reasonable behavioral modification.

There's probably some really solid sociology based studies around where this prohibition effectiveness essentially falls apart.