Yes you have, I'm sure you interact with people daily who smoke marijuana. In fact, I'm sure your boss, his boss, and his boss do a drug of some sort. If you don't think it's ridiculously common, you're fooling yourself more than you could imagine.

Nooo. You said "I've never met one that has contributed to society." Which is different than "I've never met a pot head." That being said....I'm sorry you haven't met a pot head that holds it down. Some of the nicest, coolest people I have met have been stoners.