Prohibition of anything whether it be: 1.) Boomsticks 2.) Getting your freak on. 3.) Booze 4.) Chems is going to merely allow for a wider black market. It's like Abstinence only sex ed, in that it merely tells a kid "NO!". It doesn't explain that having constant sex with multiple partners will create a plethora of disease and that using protection and sticking to the same partner will reduce the risk of pregnancy/STD's or that sex is not an absolute evil thing and within responsible use can be perfectly natural and healthy.
What a person does to their body (and each others as long as it's consentual and of legal age) is their business. Now, I think cops, surgeons, pilots, etc. should be restricted from drug use (or maybe be randomly tested to see if they are getting hammered on the job, maybe even evaluatiosn to ensure they haven't smoked themselves retarded while they're wielding a scalpel, gun, or what have you) seeing as their jobs involve life and death decisions. Some janitor or art teacher is a different story. And Esquire is right, the junkies I've seen tend to be a danger only to themselves than others. While there are cases where this is not true, it's an exception, not a rule for the most part.
The reason we have junkies mugging people as much as it is, is because of the fact since we declared a war on drugs, the prices/potency/addictiveness of cocaine, heroin, etc. have sky-rocketed. If we legalized pot and other drugs, we'd see a lower price, even a tax on it wouldn't be so bad, just make it so it's not profitable to have a wide-spread bootlegging operation. I personally am not a big drug user, though I have dabbled in the past with weed and pain-killers when I was younger. Hell, any teenager (except dorky trekkies and clueless goths) who say they haven't: Had sex, smoked weed, drank beer, and any other devious behavior, is lying out of their arses! Hell the last two presidents were big time partyers back in the day (and from soem of Dubya and Slick Willies speeches, I'd say that "day" was most likely yesterday).
I'm a smoker and I know it's bad for me, but it's my body. What I put into, on around through and/or in the vicinity of it is my business as long as I'm not hurting anyone else or creating a neglectful/abusive home for my (thankfully hypothetical) kids or dependents.
Ever notice in countries where drugs and alcohol are widely available to people there's not as bad of a case of kids drinking themselves to death or ODing? Maybe it's because that will also help take away the taboo appeal drinking has. How many of you guys remember that when you hit 21 (or for some of you old timers 18), drinking wasn't as "cool" as it used to be? Prohibiting something makes it seem romantic and exciting. After all, why do you think Han looks way cooler than Luke's whiney arse?