I don't think for a second that the use of marijuana would go down if it were legalized. People are getting past the whole stage of "Oh, what a thrill because it's illegal." It's more likely that people smoke because it makes them feel better, either physically or mentally. It is most definitely a gateway drug. People like the high. Thereafter seeking out an even better high from another substance.
Do I think it should be legalized? Hell no. Too much shit can go down during deals and I'm more than happy knowing that I'm not surrounded by that bullshit. I'm tired of being out driving and almost getting nailed by some dumbass hotboxing his ride. It's just as bad as drinking and there are laws involved with that as well.