A few people have missed an important fact; Legalisation =/= Decriminalisation.
Nice to see two or three posters talk with some kind of experiance, rather than friends of friends BS. I, like most, know plenty of people who have partaken in pot and on the rare occasion, so have I. For those who can manage the psychologically addictive traits of marijuana, then good for them. There are loads of people out there who can't and their life goes down the drain as a result.
Now, I get sick of hearing "Tobacco and Alcohol are legal, so should pot". What a load of crap; just because people got together and decided it was OK to use those drugs doesn't mean it was a good idea. I drink a fair bit; do I need to? No - I enjoy it - does it impact on my life? Only financially. It is addictive, and I am aware that it's something I've got to watch. Fortunately, I can prioritise; I don't drink when I've got to get up a 8 and go to work/uni. Some people are less able to do that. Given another opportunity, who seriously thinks our society wouldn't have been better off if a few hundred years ago people decided that these were all bad things so, now, they were gone?
I support decriminalisation to a point. Damning people with a criminal record for possession is rough - as long as someone has so little as to only be enough for personal consumption, police shouldn't be able to charge someone, only confiscate it. As for within your own home, people should be able to have a couple of plants - not enough to be able to set up a business selling it.
Another common argument is that people should be able to do whatever they want with their own lives. I ask those people, as long as a crime doesn't infringe on someone else's person or property, it shouldn't be a crime? If you're on a road with zero traffic, travelling through a rural area, you should be able to drive however you want and the EMTs can peel you off a tree later?