People smoking marijuana isn't gonna go away anytime soon, nor is the sneaky, never-ending supply... so, might as well just legalize it and tax the hell out of it.
That's not really a good argument, in and of itself. Burglary isn't going away anytime soon either, but we still have laws against it.
As a libertarian-esque, I should probably be all for legalization of all drugs and have faith in personal responsibility, but I know from experience that people aren't always responsible enough and that even the best of us can be trapped by addiction.
I believe that the rights of life, liberty, and pursuit of happiness are in a hierarchy -- in a bind, liberty is more important than property and life is more important than liberty. I have the liberty to raise my hand up and pull my index finger back, but not if I'm holding a gun and you're in front of me. Liberty can be restricted in order to protect the life of others (that's why I'm against public smoking, though I'd rather it didn't have to be a law). The question then is whether it should also be restricted to protect your own life. I'm not sure.
From my limited research, it does seem that marijuana is less dangerous than alcohol, but I have to wonder whether it would open up legalizing everything. Once we've legalized one drug to meet a budget shortfall, the government might get addicted to legalization. If it is legalized, it shouldn't be for money; the government's spending too much already.