I think it's funny how negative some people are in here about this idea. Who's to say everyone would go crazy and binge and that thousands of addicts would spring up eternally? I'm willing to bet most of the people who would be addicts are already some sort of addict to some degree. Addicts exist, the world goes on.
Yes, many people would likely become addicted overnight, but this is a natural reaction to being repressed for so long. This is why a starvation diet doesn't work. After a while, you're going to eat, and when you do, it's going to be A LOT. And you're going to have a stomach ache big time. Same idea.
After a while though, drugs would just be like alcohol. Just because alcohol is legal, doesn't mean that everyone's an alcoholic. Eventually it became more or less looked down upon to wake up and start drinking (in Planet America that is 8) ). It's not a good thing whether it's legal or not. Same thing would happen with meth, heroin, weed, etc. Most people have the will and the dignity to not be fucked up 24/7. Of course, just like there are alcoholics, there would be drug addicts. It's just the way it is.
I totally and fully support total legalization, and it's likely that I would go crazy at first, but I believe I'd be OK in the long run. Maybe I'm just crazy-optimistic
/Rant