Is ouiji board bad

Ouiji boards are harmless as long as the users know how they work. Spirit boards work on a psychological principle called ideomotor effect. There are no spirits or demons involved. Basically, the body moves according to the intent of the user(s). To get a spirit board working you (or at least one of the users) has to expect the pointer to move.

Once you and some friends get the pointer moving you'll notice that it quickly spells easily recognizable Words and misspells any Words that you would misspell.

For more fun, have someone change the orientation of the board while the users are blindfolded and then record what they spell.

Wikipedia has a good article on Ideomotor Effect.