Even though California will finally begin allowing the sale of recreational marijuana on January 1st, 2018, a lot of people are very nervous about how that is going to go. The state has had a largely unsupervised medical cannabis program in place since 1996 and now is trying to impose a strict regulatory regime on an enormous population of entrepreneurs and criminals, many of whom have never followed rules before.
To fund the oversight of recreational marijuana, California is imposing a combined tax of up to 50%, which may push users back into the black market where plants do not have the same strict safety standards. Expect some turmoil prior to the enlightenment.