An intelligent, wealthy, employable person can dabble with them, have a good time, and usually get away with it. Should they get addicted and screw up their lives, they can usually get help and bounce back without permanent consequences.
People who're a little less well-off intellectually and economically aren't so resilient. Should they get addicted to hard drugs and screw up their lives, they usually don't bounce back from it - their lives are ruined forever.
Since HN is full of intelligent, wealthy, employable people, the comments on this thread don't surprise me a bit. And yes, I agree that drug policy in the United States could stand to be reformed a little. But when evaluating the harm a person's actions can cause to society, I wish people would think a little more about not just themselves, but that vast chunk of society that's not lucky enough to not be as privileged as we are.