The concept of wandering spirits seems to be ubiquitous across cultures.  While most will say they don't believe in ghosts by the light of day, this stand gets a bit less firm in the middle of the night when strange things happen.  Why do we tell ghost stories?  They are told all around the world and continue to be told over the years so there must be a reason for their existence.  Do we all just like the thrill of a scary story, or are there larger societal reasons that we cling to our ghost stories?