Unfortunately, there is lots of money being made by keeping grass illegal. If you look at the organized opposition to Prop 19, you will see the various industries that owe some or all of their income to the War On (some) Drugs.
Pharmaceuticals, Beer/Wine/Liquor producers, private corrections companies, companies who build new prisons, lawyers, prosecutors, and judges who make a living litigating drug cases, companies who arm and equip police forces, politicians who use the drug war as a convenient means to whip the public into a frenzy, and the illegal growers themselves, who don't want to see a $500 ounce selling for less than $100 including taxes. And then there is the wood pulp paper and petrochemical industry, which is largely responsible for the illegal status of the cannabis plant in the first place.
46% is pretty good, though, and I hope they keep up the effort. Maybe in 2012, with a presidential race being decided, they can get out more of the youth vote that they need to push this through.
