Well, this is an interesting topic! I personally do not use MJ. I drink a little, and smoke ciggarettes, but drugs (hardocre or not) aren't for me.
My fiance, Trevor, is an avid smoker of MJ, and it bothers me. He is good to me in every other sense, but he has memory problems. He doesn't always remember the little things I tell him. He's losing his memory to the extent that he can hardly recall the things we did when we first met. Worst of all, he denies having any problems. He thinks his memory is fine, but it's not.
It hurts when I say to him, "Remember when we.....(fill in the blank)" and he'll say, "No, when did we do that??" Then I get called the 'crazy one'.
I love him dearly as he is, I chose to date him as he was, and I will never ask him to give up something that was in his life long before I was; but I suffer. It's said that the only person a 'drug-user' hurts is himself, and that's just not true.
I am scared someday I'll get in trouble with the law for knowing him, dating him, living with him, and for loving him. That is the main reason I am in favor of legalization... if people can't take life being sober that's their decision, but their friends and families shouldn't be at risk of getting 'caught' (guilty by association).
That's just my opinion on this subject, and I do have much more to say... but I'm supposed to be working! Interesting views, you guys! =)