Ouija boards are basically asking someone outside yourself to give you
answers. The trouble comes in because people who can ask and hear don't
need to use a Ouija board (and therefore know who they're speaking to
-- God or spirit guides or angels usually) and the people who need to
use them have no clue whether they're speaking to their guides or an
earthbound or a demon or what. It's akin to posting a sign in your
front yard that says "I want to talk to anyone who's interested" and
leaving your front door open for someone to walk right in. You have no
clue who's going to come through that door or what they're going to do
to you before they leave.

You should not use ANY tool of
divination without thorough study and a comprehensive understanding of
how it works and what the possible implications of it's use are. They
are tools, not toys, some of them can be dangerous when handled
improperly and all take years of study to master that you can be
reasonably assured that the information that is coming through is both
accurate and properly interpreted.

Just for the record, the last time I used one of these, I got an answer, that quite frankly is the only time I've ever left a haunted place a bit on the shaken side.  It's a fairly long story.  If you want to hear about it drop me a message and I'll tell you the story.  I will never, ever, use one again.  I don't think it was evil, but it opened up a memory I surpressed for years...not a fun thing.