Players as protagonists and villains

Ever since I read someone's post proposing Silverscreen Adventures, (http://www.indie-rpgs.com/forum/index.php?topic=22692.0) I've been thinking about how to make PTA play more like a movie. One convention that sparked my interest is that, even in TV shows, the villain often needs the same conflicts and development as the protagonists to give the audience reason to either hate them or sympathize with them. In PTA, the producer's job would be to present situations in which the protagonists and the antagonist(s) have opposing stakes, but other elements threaten both of their stakes. (The hero and villain are fighting atop a moving train, for example.) These conflicts can build throughout the series, and we can even watch as one of the would-be heroes slowly descends into villainy. Heroes is a show that obviously adopts this style.

I'm curious what everyone else's thoughts are on this, and especially would like to know if anyone has tried it in their game.

- Nick