@Skinny-Love and @Bullet, really good and interesting conversation going here! You both bring up really good points. I would never claim to know everything (especially about a bottomless topic like the spiritual world) so I'm glad for your posts and thought provoking questions/ideas.
The reason I said the spiritual world should not be messed with is because it is real-- I don't mean to negate that by disregarding the term "ghosts". I guess what I believe though, is that the spirits of people do not stir from the grave on their own or for good reasons. I believe it's foolish and evil to attempt that, but (as you've pointed out) I really have no idea if it's possible, or if demonic principalities just deceive those that try into thinking they're powerful enough to do so. The one thing I do know is that seeking the spirits of the dead is brushing shoulders with the demonic, and is a gateway for evil-- which is why God told us not to mess with it.
You both have answered each other pretty legitimately so I don't want to butt in, but do want to thank you for the dialogue and scripture references. This subject needs to be talked about more, people are either dim or fearful about it and Satan takes advantage of both ignorance and fear.