One of the things I loved about this movie is a look at how powerful psychology plays a factor in people's minds. The psychological impact of a skilled preacher, combined with stirring worship music, surrounded by a crowd of other believers, the preaching and/or music gradually increasing in volume and tempo, is very overpowering to a lot of people. This is the state when people are most vulnerable and susceptible to power of suggestion and other forms of trickery. This is also the state where people will believe anything, even with any form of trickery being absent.
In fact, I remember one clip where Marjoe was touching people, who were all lined-up, on the forehead and then they would fall down. Now this one lady was next in line, and wanted so badly to fall down that she was literally shaking, her whole body was just shaking, waiting for Marjoe to touch her head. Once he finally did, that gave her all the excuse she needed to flop to the ground and start shaking. (Now I'm just shaking my head remembering that little clip.) The picture to the left is not that lady I just described, but just another lady.
In addition to exposing faith healers, Marjoe also briefly explains another phenomenon, speaking in tongues, and how that is done. I just can't stress enough the importance of seeing this documentary, regardless if you're a believer or not. Just watch it!
Here's a link for a little more info - http://en.wikipedia.org/wiki/Marjoe