I am very undecided on this issue. I believe that it should be available for medical use, that much I'm sure of personally.
As for recreational, I can understand the idea that regulating it could have some benefits, and I do feel that some people are being imprisoned that shouldn't be due to what I consider minor offenses.
But I also worry about the long term effects, and I worry that so many of the studies that I read seem to be biased by whoever funded them so I don't feel like I'm smart enough to accurately know what the effects are. Coming from a family that deals with addiction issues, there is parts of me that wishes none of this was legal, no alcohol, cigarettes or marijuana but I know that is foolish.
I have asked my children to wait to start. I've told them (in a joking voice) do anything you want when you turn 25 but promise me you'll wait until then lol. As for the kids - the message they are being told at school is that their brains are still developing and any chemical can have negative affects so they should wait - and at least to me, they say that makes sense and that they'll wait. We'll see.
On a slightly different note, I'm curious what legalizing marijuana across the country would do to the drug trade with Mexico. I've seen articles that already state that legalizing it in some areas is messing things up in Mexico. I wonder how that would make things change.