I was assigned a mentor through one of the interest groups at my medical school. When I went to shadow her (she was an intern at the time, I was a MS1), the attending looked at me briefly and said, "You're not going to write down everything you see and put in on the internet are you?!" At first I asked if he was kidding, and then jokingly asked if he wanted me to do just that. But, apparently they had some undergrad shadow the week before, and kept notes on everything that happened. He then posted his whole experience on the net including the patients names, what they came in for, and what happened. Needless to say, anyone with half a brain wouldn't do that, but as long as there are people with less than half a brain, docs will err on the side of caution.
If you really can't find anyone to shadow, then you can volunteer at an Emergency Dept. When you're there, just tell the nurses and docs that you're interested in medicine, and if there is anything interesting going on you'd appreciate it if they would grab you. If you can volunteer at a teaching hospital, then the docs will be more likely to remember that you're around. Otherwise, you'll just be changing sheets and transporting patients as a volunteer. Good luck.