The well-respected British conservative/libertarian magazine The Economist (in my opinion the best world news source out there) argues in favor of legalization of all drugs, calling it the "least bad" option. They note that it's not a desirable outcome - just the one that does the least harm compared with various models of prohibition.
Note that they don't just favor legalizing marijuana or the less dangerous ones. They want it all legalized, taxed, and regulated. Their argument is extremely convincing (of course, convincing me of this point is not hard to do). They've been arguing this for the past 20 years, but there's reason to believe that now that the country with the world's 13th largest economy has become a war zone, people might be willing to listen.
The world needs U.S. leadership in this endeavor, though - it's mostly our willingness to fund anti-drug efforts in producer countries that keep drugs illegal through much of the rest of the world (this is certainly true of Latin America). Obama has political capital up the wazoo right now - what better way to use it than to end the misery of the war on drugs?