In reality however things are not quite that
simple. Firstly, not everyone can get the ouija board to work. At least
one of the people present has to have some intuitive/psychic sensitivity/ability.
Even if he/she doesn't know that they have this.
(1) A positive person who is physically dead and helps/guides people. Often termed a "spirit guide" of the Light.
(2) The opposite of (1)
(3) Someone who is physically alive but may be outside of their physical body (OOB). They could be a positive person, negative, or somewhere inbetween.
(4) Someone who is dead and doesn't know
it. What many people would refer to as an "earthbound
person".
When one considers that a sitter may be intentionally, or unintentionally, moving the pointer themselves (without any spirit input) then one can see that there are quite a number of "options".
Can one tell when "communicating" which of the above is the correct choice ? Yes, but to do that one would need to be properly trained in the area of mediumship. Most people who use ouija boards are not so trained.
You might think that if that is all that can go wrong with a ouija session then as long as one doesn't take things seriously then there is no harm done. Unfortunately that isn't the case. When one sets up the circumstances where spirit people can communicate with physical people then a group of spirit people will assemble to do just that. If some/all of these people are negative then they are the sort of people that you may not want to attend at all, let alone "hang around" afterwards.
Simply finishing the session doesn't mean that any of the discarnate people will leave the area. Some of these people may decide to stay around one, or more, of the sitters for years and/or stay around the room/house the ouija session took place in.
This alone would be likely to precipitate a number of negative experiences for people but as if that wasn't enough even worse can happen. One, or more, of the sitters can end up with spirit obsession/possession problems. Need I go on ? Perhaps it would just be easier for me to say "Unless you are a properly trained medium then have nothing to do with ouija boards."