For me a ghost is what the mind creates as a reaction to a stimulus which no longer has a viable "mental landscape" in which to be rooted.
I'm dancing with a story about an idea very much like this at the moment. I would not be surprised if this has something to do with it (the phenomenom).
I think that's what this is all about, religions, ghosts, whatever. People like the story with the tiger better. They like it so much that they're willing to overlook fantastical and improbable things. Most people want there to be ghosts.
Way to paint all things you disagree with with one stroke.

Regarding IP's pictures, the much more likely explanation is, as Delta-9 is saying, something material or some trick of photography. But there are more seductive answers...
trick? i have nothing to gain by faking this. i repeat: it happened several years ago.