It is rare.

The human being is built in such a manner that this sort of thing is possible. 

However, most often, when people think that someone is possessed, it is usually the case that either (a) the person is acting according to their free will and other people around them refuse to accept that, or (b) there is undiagnosed mental illness (and often an unwillingness to look into the possibility of mental illness due to fear of stigma). Of course, all these things can work together, but don't blame jinn for things that are not their fault!