Here is an interesting little thing I found online a while ago. According to the article, a trained Psychiatrist and a team of Catholic priests and nuns actually witnessed a real life exorcism! That's right- not one of those phony baloney ones done by those protestant nut-cases; but a real, true blue one! Just like the film the exorcist, the team reported several strange phenomena including: Levitation, Super-human strength, clairvoyance, Xenoglossy, and psychokinesis.
Amazing huh. The only problem is... they recorded none of it! That's right- all these crazy things happened, and nobody ever thought, just for a second, to actually use a video camera. Furthermore, the only two news sources I was able to find this incredible story on were "New Oxford review", an exclusively Catholic magazine, and "World Net Daily", a bunch of hyper-conservative right wing Birthers. Beyond these two very questionable news sources, we haven't a shred of evidence that any of this actually happened.
Furthermore, even if we were to use these sources, the pertinent details are severely lacking. They briefly mention some of the supernatural happenings in passing, but that's all. For example, they report that objects "flew off the shelves on their own"- but they never tell us any of the details, like exactly which objects did so, or how they could tell there where no naturalistic alternatives. The worst part, however, is that these articles never even tell us the identity of the woman being possessed. If this case were to have had no paranormal phenomena, than I could imagine her being afraid of accusations to her sanity. But supposedly psycho-kinesis and levitation occurred! Surely any un-justified criticism by pseudo-skeptics would be deflected by eager parapsychologists. Super-naturalist friendly America would have embraced her- not ridiculed her. But, once again, the biggest problem with this case isn't the lack of evidence per se, but the fact that, had this event actually occurred, we should expect the evidence to be a lot better. The fact that the details are so sorely lacking is either the result of very poor scholarship- or very deviant fraud. Or perhaps both.
After all, naturalistic explanations can be applied to several of the purported "supernatural occurrences". Tricksters have been known to move objects in order to deceive others- which is the cause of many poltergeist cases. Furthermore, Pseudo seizures sometimes produce violent movements that can be confused for levitation (a short discussion on this can be found here). Furthermore, the intense emotional stress these types of events generate often lead to mass hysteria, in which strange collective delusions can form. Michael Cuneo, a skeptical sociologist, sat in on over 50 exorcisms while he was writing his book "American exorcism- Driving out demons in the land of plenty". During the events, many strange things would be reported, such as levitation. Cuneo, however, would be unable to see the phenomena, even though others present could (see here and here).
So in conclusion, I think we can safely say that, even if exorcism does work and demons do exist, we simply have no way of finding out until more serious research is done. It's just a shame that it will most likely end up yielding no results.