I'm not sure why you believe marijuana users are likely to endanger others. How many have you met? Police officers say marijuana users tend to be the easiest people to arrest -- they're less likely to fight or cause problems than drunk people or meth heads.

The biggest effect this will have on our society is the dismantling of the Mexican drug cartels and the ending of the War on Drugs. This will obviate the need for hundreds of deaths and hundreds of thousands of arrests each year. A large percentage of the US population will no longer be criminals for recreationally using an intoxicant less harmful than any legal intoxicant, including alcohol.