One thing that people aren't considering is that we have legalization experiments within the United States, and we have seen an uptick in marijuana usage[1]. This uptick has been benign because its been limited to Marijuana. I think that given our culture (one that I believe is potentially universal, but I can not speak to universality) has a tendency toward over consumption, its not clear to me that legalization of drugs would lead to decreased usage. I'm not advocating continuing our failed drug war, just caution when considering legalization, it may still be the best way forward.
[1] http://www.rmhidta.org/html/FINAL%20NSDUH%20Results-%20Jan%2...