First there is a god, and anyone who has done a séance can not disagree with this as they have come into contact with a past spirit, so there is life after death, so there is a god. You can't pick and choose between religions.
Second god does not allow the use of ouija or any witchcraft. That involves tarot as well, if you place your finger on the ouija glass or tarot or whatever, you are inviting a spirit to enter our world, once here they most likely do not go back to where they came. They stay and stay around you.
The spirits goal is to take possession of you, the more you use the ouija and other forms of "spirit channelling" the more likely you are to be possessed. At first the spirit will be nice and will try to entertain you perhaps pretending to be a lost family member or friend, all the time trying to buy time so they break you down to possess you.
Once the spirit is inside you might not even know it and if you do, the spirit is happy to go along with what we do as it "alive" again.
Once asked to leave though, the spirit becomes angry and confuses our thoughts and puts angry and violent emotions into our head, this can lead to madness.
The spirit may however never reach this stage and it may stay on the ouija, after time this is where you see the real side of the spirit as it is angry that it can't possess you and it will become rude and violent.
People should know that you very very rarely contact a "familiar" spirit which is not a bad one, the others are demons and evil spirits.
People talk of séance's conducted alone. This is dangerous as since it is only them, the spirit has a much greater chance of possessing them.
All I can say is that all forms of witchcraft are not bad, they are tools of the devil made to attract you into using them so as to bend and eventually break you. This one of the ways he gets back at god.
If you want to read know much more on this go to http://www.spiritualcuriosity.com.
Remember this though: when you put your finger on the ouija you are asking for THEM to TALK to you, they have controll.
They choose you, you don't choose them no matter what they say.
skeptika's note:
I get quite a few of these. This one is actually a little more balanced and reasoned than most. Still though, I would like to see more evidence to support the contention that spirit's are almost without exception trying to possess ouija board players. I know a lot of people and none of them are possessed.
Where are all these possessed people hiding?