Can ouija boards be dangerous?
It depends if they work. If they do, you will have to worry about making the spirits mad, which can lead to numerous results. Also, you have to watch out for demons or the Devil, trying to trick you into thinking you're talking to a "ghost".
The use of a ouija board in essence opens a channel from the "other side" to the person working with it. if you are an experienced practitioner of magic you have learned to create and maintain a spiritual shield. This can and does protect you from unwanted/uninvited spirits and spiritual entities, which may attach themselves to the user. Inexperienced, and unprotected users can open doors to some very scary things, so yes, the use of a ouija board can be dangerous.