What is really funny is that some people consider this as EVIDENCE that ghosts exsist. They go into a dark room and randomly take pictures and when something weird shows up, it is PROOF that the place is haunted and there are ghosts. When in reality you are passing light through a camera lens that has multiple elements, many of which are coated with different things, thus resulting in easily explainable abnormalities. IE in low light situations (which is usually where these nut jobs take photos) lens flare is a horrible problem, add in the cameras flash and the reflections off of things makes flare even worse. There is an actual term called "ghosting" where in cheaper camera lenses the light doesn't go straight through the lens, but instead has a tendency to bounce around off the lens elements (particulary noticable in night shooting situations).
Sorry, I have a friend that likes that show ghost hunters and they love to do this nonsense. All it shows is they need better camera equipment.