Federal authorities may raid California's medical-marijuana clinics with regularity, but that hasn't prevented the programs from generating $2 billion in annual sales and $100 million in state tax revenues, the New York Times reported May 31.

California has about 500 marijuana dispensaries where individuals who use the drug medically can get their supplies. Setting up a dispensary can cost up to $100,000, and legal fees can be steep, but many seem to be surviving and even thriving.

There's even a medical-marijuana trade school, called Oaksterdam University, in Oakland. Here, students can learn everything from the politics of medical marijuana to botany and how to run a small business. "The investment is well worth it, except for the federal risk," said Jeff Jones, the school's chancellor.