And that's exactly why the government would have such a hard time taxing it. Unlike tobacco, it's extremely easy to grow for almost anyone anywhere, and pot-smokers are wary enough of the tobacco companies that they would have a very good reason to do that if weed were legalized. Heck, I wouldn't just grow it in my backyard. I'd plant seeds everywhere I went, to spread the plant as far and wide as I could. With so much homegrown stuff about, it would be very difficult for a few companies to dominate its market as with tobacco. I suspect most of the people who didn't grow on their own would just go to the existing local growers, who would just move their operations above-ground.