You know, I can't help but be reminded of the movie Layer Cake ( http://www.imdb.com/title/tt0375912/ ), where the main character, a drug dealer kingpin, points out that drugs will be legal some day, and that people like him are just ahead of the curve as far as making a business out of giving people the drugs they want.
Thinking of it from this angle, if drugs were to indeed be legalised (as in, like cigarettes - not just decriminalised), the possibilities for innovation, product development, etc, would be pretty enormous. You want to build a product that people just keep coming back to? Here it is.
Sure, eventually, this market would become like food or, at best, cigarettes - with smaller margins, and not much innovation. But it would take a while, I imagine, and in the meantime, there would be a lot of potential innovations, experimentations, etc.
Just a thought...