latest issue of Readers Digest talks about the addiction problems in teens using Marijuana.  It's a becoming a major problem because there is such a rush to make it legal and anybody who nay says is attacked.  There is a refusal for treatment as there is a refusal to admit that there is an addiction possible. 
The changes in the brain in the young is significant as are the results of prolonged usage.  In addition today's drug is much more potent than the ditch weed of the 60's. 

The states are looking at billions of tax dollars and as usual don't care about the well being or safety of the population.

And remember, making it legal in your state doesn't make it legal in the USA, so as a drug user you can lose certain rights that the federal government currently recognizes.