Ghost don't exist, or rather their existence is dismissible in lieu of evidence. I've had people call me 'narrow minded' for that but in my opinion it is they who are 'narrow minded'. I am 'open minded' because I am open to the fact that it requires more than my own mind to discover the truth of something. The complexities of genetics or the vast amount of credible history out there is infinitely more interesting, deep and complicated than stories about ghosts. To me the reason people believe or even see Ghosts is they desperately want for the universe to have magic qualities when the truth is the material world is much more 'magical' and wondrous than The Shining or The Exorcist.
This is not to say Ghosts and Ghost walks are not tons of fun, and that a finely crafted ghost story isn't worth applauding. It astounds me though how many well meaning adults who will demand evidence for computer purchases and auto-repairs will abandon that same method when approaching much bigger and much more fundamental questions.
These superstitions and folklore probably served a great purpose to humans isolated and sanding in search of food. They probably brought cohesion and obedience, but the fact that we have this discussion and it's not one sided at least goes to prove that a lot more doubt has been cast on those who would consider such a thing.
It's not that I do or do not believe in ghost; simply that I know I have yet to uncover any credible evidence, first hand or otherwise. Even if some of the forgeries or vague bits of evidence turned out to be valid: who cares?!? Ghosts don't interact with us in any meaningful way. If a ghost opened my door I'd shut it. Seems like every ghost exists simply to perpetuate the minor inconveniences we experience on a day to day basis anyways. The discovery of a ghost would have to match the routine, mundane paranormal activity-esque ghosts we've seen on TV, anything much worse could not necessarily be considered the same phenomenon without evidence linking it with past ghost encounters.
Which brings me to my final problem with Ghosts; they are intelligence wasters. There is no greater waste of thought than trying to explain away every personal experience. Neither they nor I can repeat a reported ghost encounter. They are inherently first person, unlike science which attempts to minimize personal bias and the spotty record of the human brain. Cindy may claim to see spirits, but the fact that she's lived to tell you this tail probably means they are not very dangerous, and if Cindy was more skeptical about herself she might not get wrapped up in an emotional frenzy over nothing. However were I to investigate Cindy's claim I would advance no knowledge about the world, only Cindy's world. I don't believe Cindy is stupid, she really believes this, but I want her to be responsible for vetting her own experience. If she takes on this responsibility my prediction is she'll discover most of her personal feelings are not indications of reality but rather simply her own personal responses to it.