First of all, pot is only drug because the laws put in place in 1937 made it so. Pot is less addictive than caffeine, nicotine, or alcohol, and doesn't have the negative side effects of either nicotine or alcohol. Furthermore, cannabis has over 200 known uses including making paper, fabric, energy, etc. In fact, the U.S. Constitution was drafted on hemp paper! Furthermore, this would end the silly war on drugs which is a losing battle which puts people in jail for victimless crimes everyday. Think of the burden that would be removed from the justice system because we weren't prosecuting people for personal possession on their private property. Then, if it was regulated, think of the tax revenue that could be generated from it. Add to it the fact that people wouldn't need to get their pot from a shady dealer who smuggles it in from nefarious Al Capone-esque characters, and you've just eliminated a large portion of the black market for marijuana. Also, if it were legal, then the government/private organizations could fund education about the good and bad of marijuana, as well as the other 200 uses for cannabis. Economy improves, quality of life improves, legal system is less burdened...what else do you want?

For more info, check out: http://everythingishistory.com/2009/04/20/interesting-stuff-about-marijuana/