Exorcism is a favourite topic of mine, becuase well, what sort of idiot, when faced with classic possesional charactoaristics would refuse to have his child exorcise. Let's face it, an exorcism can't possibly hurt more than it helps and it's really the only recourse is you are possesed.

Having said that, I don't believe demonic possesion is at all common and a number of people who claim to be possesed are probably merely hysterical.