Even if use did increase, it wouldn't increase that much, and it is still less harmful than alcohol, and you wouldn't have to spend 20 billion a year on taxes and probably make a lot off taxing it.
Yep...it worked really well during Prohibition. (/sarcasm)
redrock
That doesn't follow. You assume that there are loads of people jones-ing for pot that can't get it now. This is false on two accounts: most people who don't smoke pot now aren't interested in it, and anybody can get it anywhere. Pot is already ubiquitous.
As with a great many commodities, relative availability does not significantly affect consumption rates until the market drives the prices to ridiculous levels. The government is utterly incapable of driving prices to a level where it impacts consumption for most illegal things. It is foolish to assume that this doesn't apply to MJ.