I don't know anyone who does marijuana that is addicted to it. You never see people in rehab for chronic weed addiction. It's always the harder stuff.
Most people who are in jail for non violent drug offenses are in there due to marijuana, whether it is possession or intent to sell or whatever. If weed was to be legalized, crime would drop significantly and the jails would miraculously not be overcrowded anymore. Weed will never be legalized on a countrywide level though because they would lose tax revenues from cigarettes. Of course, if you tax the shit out of weed, you have more government revenue there, so I don't know what the issue is.