Is the legalization on Marijuana in California a good idea?

Its being called The Inalienable Rights Enforcement Initiative. From the full text of the measure:
"This initiative will amend the Constitution of California to defend and safeguard the inalienable rights of the People against infringement by governments and corporations, providing for the lawful growth, sale, and possession of marijuana. Marijuana will be taxed through a system of stamps and licenses--a $5 stamp will be required for the sale of an eighth ounce of marijuana and a $50 annual license will be required for the growth of one marijuana plant. To protect participants and encourage participation in the system, such licenses and stamps will be available anonymously in stores where marijuana is sold."
Do you guys think that this is a good idea? Do you think that by legalizing weed in California it will spread throughout the United States? Most important, do you think that taxing it will help the economy? Give me toughts.