Drug tests are counterproductive, because not only do they not dissuade drug use (empirically), but they push drug users towards drugs like cocaine, which are detectable in drug tests for only two days, instead of drugs like marijuana, which are detectable for several weeks.
The only drug you can really test for effectively is marijuana, and I frankly couldn't care less whether an employee uses marijuana - medicinal or recreational - in his free time, just the same way I don't care whether he drinks alcohol or smokes cigarettes.
Finally, it's nobody's business what an employee of mine chooses to do after work so long as it doesn't impact his work performance. If it does, that's reason enough to fire him right then and there, without any need for a drug test.
I'm also impressed by your assertion that employees will think, "Shit, I can't smoke weed, guess I better start doing coke!" It's like the whole "gateway drugs" thing, except he skips straight to the hard stuff because the gateway isn't available to him.
In my personal experiences, I'd have to agree with Steve and I personally would rather hire someone who has taken LSD vs someone who hasn't. To me it doesn't show irresponsibility- it shows a sense of exploration and creativity.
Exploration? perhaps, but boredom and peer pressure are more likely explanations.
