I think there is a lot of BS stories and people can have over active imaginations. That being said, I do believe these boards can be a tool for evil. I was raised in a very strict Catholic traditional household. We were told Ouija boards were tools for the devil. Both at home, and at Catholic grade school by the nuns, etc.
I remember going to the toy store as a child, and I'd grab a Ouija board and ask Mom if we can get one of these as a joke. She never saw the humor (sorry Mom).
For years I never really believed it though. I've talked to quite a few people about them over the years, and how they have had weird experiences.
I tend to believe it now. Not in my home will I allow one. I figure it's like the front door to your home, but a door to the spirit world. If you willing leave your front door open and invite any and everyone through, you don't know who is going to come into your home.
I think Ouija Boards are bullshit...nothing but pieces of plastic and cardboard. Evil lies in peoples hearts and minds. If you summond that evil, it is not coming from a silly cardboard game.