Ok, now that I've said my peice about analogies, let's just for a moment assume that the analogy "players are like actors and characters are like the roles that they play" is a good one. One of the things that struck me as most bizarre about the writer pushing the analogy is that he begins by stating "We gamers commonly use a movie or theater analogy...", but he thereafter ignores the possibility that the analogy is of theater and not of cinema. As I've already said, I don't agree that 'we gamers' commonly use the analogy he makes, but were the analogy to be made I think it would clearly refer more to theater than cinema and that if we wanted to stretch the analogy we'd do so in the direction of theater and not movies.
The idea of the process RPG storytelling being at least something akin to the process of staging a play, makes to me far more sense than the process of RPG storytelling being something like the process of making a movie. Making a movie is as much a visual art as a literary art. Making a movie usually involves many retakes, many short scenes later edited together, and a high degree of directorial control over what actually gets commited to film. None of these things really feel to me like the process of playing an RPG. The process of staging a play however, while by no means a perfect analogy for an RPG, is at least a far better one than movie making.
In fact, to the extent I hear an analogy like this, the analogy I actually hear is to compare an RPG to improvisational theater, because both an RPG and improvisational theater feature either no script or only rough outlines and provide a very high degree of freedom to the actors to provide direction for the story. In this regard, the role of the GM is closer to the role of Drew Carrey in "Whose line is it anyway?" (or for those in the UK, Clive Anderson), in that he chooses a theme or scenario and grades the performance of the players but otherwise has a very light touch on how the players actually perform. The analogy isn't perfect, but its alot closer to how I feel running a game than George Lucas or Alfred Hitchcock or even Jerry Bruckhiemer.