People assume the marijuana today is the same as it was in the 60's. Then smoking 5% THC leaves in joints by hippy types was pretty harmless.
Modern marijuana can be highly concentrated using butane and the buds of the plants. People are producing 80%+ THC. Placing the concentrated butters and whats called dab into foods and now the big thing is e-cigerates. Think odorless "vaping" right next to you.
It is anything but the wild wood flower of yesteryear.
It took nearly 100 years to develop regulations of alcohol to an acceptable "leading cause of death in working age Americans."(link below)
Marijuana will require just as many regulations as alcohol production. To claim anything less is naive. One can make $100,000 a year producing marijuana but one can make $500,000 a year selling on the black market(illegal sales) what will some people be tempted to do?
To answer one other question, we do have a presumptive impairment amount of thc for operating a motor vehicle.
The leading cause of deaths comes from the cdc-http://www.krmg.com/news/news/local/alcohol-abuse-leading-cause-death-working-age-amer/ngTYf/
