The direct effects marijuana has on you isn't that bad...but being high can lead to an unlimited amount of dangerous situations. I've heard of and seen people do much worse things when high than when drunk. An old friend of mine (I might have considered him my best friend) attacked quite a few people once (including me) when he started doing marijuana. It changed the person he was completely...he was like one of the nicest person I knew, and when I tried hard to make him stop the weed, he eventually flipped out and hit me with his hockey stick. It was one of the saddest times of my life...I had to hold him down, he was hyperventilating and minutes later he calmed and I took him home and helped his mom take him to the hospital
I've had a lot of friends over the years who drank a lot, but they never acted like he did...they didn't
change like he did.
People can show me statistics and crap like that, but I'll always feel more comfortable seeing someone close to me with a beer in their hand instead of a joint.