I should say right up front that I do not buy into the ghost stories. None of these theories particularly thrill me either. The theory that I find most plausible and interesting is related to piezo-electricity. For those who don't know, piezo-electricity is electricity produced by placing stress on a crystal. You've seen it before in the push button ignitor on your gas grill.
Some cigarette lighters use the same principal.
I saw an old episode of 'Nova' where a guy in a laboratory illustrated the principal by crushing a piece of granite in a hydrualic press. When the granite finally gave way you could see little balls of light flying from the fracture points. If you let your eyes get accustomed to the darkness first, you'll see the breaking lifesavers illuminated by little flashes of light as you bite down on them. Well, if you consider the crushing forces in the earth, especially along fault lines where rocks and quartz crystals and all sorts of things are being crushed under tremendous pressure as the earth shifts, it could have a great deal to do with spooklights. Electricity must be being generated in all those crushing rocks and crystals.