I don't think it should be "legalized" per se. I do however maintain that it should DEFINITELY be decriminalized. The issue is not a black and white issue. Marijuana does have serious health risks, just like all vices, cigarettes, alcohol, none are without risk. I could go into the addictive properties and the marijuana withdraw effects (which are rather long 3mo - year for depression etc) I mean not everyone experiences problem from use, but then you can also say not everyone gets lung cancer, COPD, or even a cough from cigarettes, not everyone who drinks alcohol will end up with liver cirrhosis, an addiction, or under a bridge. I just think the big deal is less the physical dangers of the drug but rather the mental health risks associated with it. I think with it's decriminalization there still needs to be heavily funded (perhaps divert all the law enf. monies to this) mental health services to support the addictions that exist just as they have for alcohol. I'm sure I'll get some flames for this, but that's not the intention. I don't think it's right by any means that a single person even so much as pays a fine for a plant. Especially when the situation would be so much better served by mental health support not so called justice.
Again, nothing is black and white. Rather than arrest and criminalization (and possible institutionalization for those involved with higher levels of posession etc.), all this war on drugs money should be diverted into mental health services, addiction itself is a disease, the poison involved with the addiction is secondary to the actual addiction. Addiction is genetic with environmental secondary roots. There are actual differences in the physiology of those with addictions (not just chemical addictions, but even gambling/sexual addictions show different parts of the brain that differ from those without addictions) So none of these should be treated criminally when they're suffering from a disease. Obviously the line between criminal activity and involvement with addictive substances is thin. This has to be kept in perspective, how to treat the addiction and punish for criminal choices made while under the influence. The fact an addiction is a disease does not lessen the fact that criminal actions are criminal.