Another vote for legalization here.... This quote is from an excellent article on the failings of alcohol prohibition. Almost all of it can be applied to marijuana prohibition.
http://www.cato.org/pubs/pas/pa-157.html
"Although consumption of alcohol fell at the beginning of Prohibition, it subsequently increased. Alcohol became more dangerous to consume; crime increased and became "organized"; the court and prison systems were stretched to the breaking point; and corruption of public officials was rampant. No measurable gains were made in productivity or reduced absenteeism. Prohibition removed a significant source of tax revenue and greatly increased government spending."