I think I share Tony's dislike of the idea of the equivalent of Big Tobacco forming but around hard drugs. Nobody wants Joe Camel brand cocaine.
Are you familiar with the Washington and Colorado markets? Most of the stores function as more similar to farmer's markets or consignment shops. They get their product from small growers, and there is no megacorporations involved or marketing.
Also Tony you really need to think of the demographics of who is most likely to use marijuana with your suggestion people just "grow their own". You think college dorms are going to allow college students to set up growing spaces? Or that it's easy for hipsters who live in small cramped apartments?