The reason I belive in this stuff is quite simple. My gran is a huge catholic, very religious and an active member in the church community. She's good friends with the priest of our parish and he invites out family around for barbecues and I watched some of the World Cup matches there with him. Overall, he is a nice man. Funny, intelligent kind and incredibly wise.
one night (I think my auntie started it) we got onto the subject of ouija boards. And he simply told everybody there to never touch one, never be in the same room whilst one was active etc. this got me thinking, why not? He pretty much implied about demons and spirits and how we should never 'dabble' in such matters. I'm not the best catholic, but I listened to the priest not because of religion, but because he was obviously so (I don't really know what to out here. He said it calmly, but you could tell he was 'scared' by what he was saying.
I completely trust this man and I will never be in the same room as an ouija board. Ever.