I think ghosts are simply a man-made idea to help make the concept of death more bearable. I've read about a scientist claiming he has proof of an afterlife. About five "mediums" questioned two "subjects." When the mediums told the scientists what the ghosts told them about the subjects, everyone's information was almost identical. I don't buy this story though. Also, I suck at explaining it, there's more to it than what I've said.
If ghosts aren't real, or if they are and all they can do is make little dots pop up on my photos, it's not going to matter to me. Either way they don't really affect me, so it's hard to have any opinion other than "wut?"