> This, BTW, is what happens with medical marijuana. There are people who really need it, there are people who think they need it, and then there are people who who tell everyone but their doctor that it's recreational.
Well, yes, and this is how it came to be allowed; the harm from the "preventing recreational use" system was so huge (see yesterday's war on drugs post etc) that it made sense to stop trying to make this distinction. The medical system provides a "fig leaf" which allows the remaining pure-puritans to accept it while at the same time the people who need it for medical use can get it, and nobody has to get their life ruined with jail.
(By "Pure-puritans" I mean those people who are against it because it's recreational, not because of alleged harms or externalities like smoke)
I also think there's a huge grey area of people with chronic pain or unhappiness problems that don't quite reach a diagnosis bucket - or they've not yet learned to speak the words that would get them there, or don't meed the social class critera - whose "drug seeking" behavior might most easily be addressed by just letting them have the drugs. As long as they're not opiates.