Saw V, the newest movie in the cash-magnet franchise, is not exactly a big deviation from the concepts set forth by its predecessors. While the movie's twists and turns are definitely out there, and in some cases might even be getting a tiny bit redundant, the real draw power of these movies comes from the mind twisting torture scenes and the idea that people could be put through these demented sort of games in order to be taught a lesson.
It is a kind of guilty pleasure for both myself and people I know to go to the movies and see a man being cut into multiple pieces in a sort-of "Pit and the Pendulum" style moment. Granted I wouldn't do this to anybody else, and you can be sure I don't want a draft going through my midsection, but there is without a doubt a sort of perverse fascination with scenes of typical people doing these types of things to each other. I think that the reason people can't get enough of things like this comes from the fact that we really can't see ourselves or other people doing these sorts of things, so when the images are put forward in front of our eyes we are forced to associate with these acts in ways we never really wanted to - essentially it allows us to live vicariously through the movies and characters portrayed on the big screen.