What does society have to gain? How about organized crime's profits being completely undermined. Government agencies profits being completely underminded (how many billions every year in the War on Drugs?) The guys clear-cutting our forests profits would be undermined-hemp makes better paper. And the economy in general would have to make some dramatic shifts. It's the first, second and third largest mony crop in a lot of places. So basically, just like everything else, if you want to understand something-just follow the money. That works for almost everything from Marijuana to Iraq.

The down side? I think the Culture would fall away. It wouldn't be cool and rebellious anymore and most people would loose interest. As it stands now it's something of a beckon pointing out our society's corruption, hypocracy and greed. Joe Average is being persecuted and becomes aware of Big Brother's tyranny. I think we would loose that and a lot of people would put their heads right back up their asses and fall into complacancy, blindly doing what 'The Man' wants and never thinking for themselves. You wouldn't be cool anymore, you would just be stoned.