http://www.huffingtonpost.com/dan-sweeney/taking-the-pro-pot-positi_b_179653.html
It's a good blog post by Dan Sweeney, and I tend to agree with what he has to say about legalizing marijuana.
I do have one caveat though: There has been enough study about marijuana to know it its effects, addictive qualities, outcomes, etc. Is it conscionable to legalize, tax, and put age limits on something we know is harmful? The argument I see is, well, tobacco and alcohol have been legal for decades (except for Prohibition, but people still drank... wood alcohol), so who cares, right? People should make their own decisions and if it's harmful to themselves, well, so what. They made that choice.
However, I don't think it's that easy. Cigars and cigarettes are heading the way of the dodo. Slowly, but it's happening. With so many restrictions in place, it's not cool any more to smoke cigarettes. Sure you still see a bit of romanticizing, but more and more places are placing smoking restrictions, so if you even try to light up, you're gonna get harassed.
Alcohol is a bit different. There are way too many variables for this one to ever be handled properly. You've got the fact that it is one of two things you can't do when you turn 18, you have organizations like MADD promoting a designated driver, but people still die everyday due to drunk drivers, you've got hundreds of different types of alcohols running around, and you have teens drinking like it'll be gone the next day. If you ask me, it's not taxed enough. It's more like price-inflation to make some profits.
So now we have two legal drugs and their various forms that we've had legal for decades and have known for years are damaging to our health. Yet, they're legal and you can go to most countries and 49 states to get them anytime. I just mentioned the most striking difference between pot and alky/smokes: The latter two have been around longer than we've known the full extent of their damaging effects, and it is the exact opposite for the former.
Now, I believe that if marijuana is legalized, taxed, and set with age limits, you will see the rate of arrests for nonviolent drug offenders drop significantly. It would be a revenue source, especially in California. However, you will still have home-growers and black-market purchases. I don't see much changing, except producers may come to the public view for added revenue themselves. So if that is the case, should we allow more people access to the drug who wouldn't otherwise get it? Would it be in good conscience as a society to present people with a known harming agent (other than war and guns)?
Perhaps, yes, since marijuana is the least of the drug worries. And perhaps, yes, since there are bigger things from which to die or be harmed, so what's a little more government revenue to sweeten the pot?