Let me tell you what kind of role I see for the GM -- that is, what kind of GM I try to be -- and then you can get on with the business of denouncing my heresy on RPG.net and the burning in effigy and the voodoo.
I believe in a strong GM that leads the game with powerful but open elements of story. I think it is the GM's explicit job to create drama for the players, pushing them to their limits and driving them to make decisions that reveal and change their characters. Sometimes, those elements of drama and story should even be things the players might not necessarily want for their characters.
Controlling, manipulative heretic. Yeah, I know.
Here's why I think that: the GM is in a unique position among players at the table (and yes, that is another one of my beliefs - the GM is a player). Although in our "house" style of play -- High Trust, High Drama -- the players are both actors and audience, the GM is in the position of being the audience all the time. He observes the game as it unfolds from a particular position (he is not one of the main characters in the game, married to a particular point of view) where he is uniquely qualified to assess the "Big Picture" of the game. How does it all fit together? Who needs more spotlight time? What does this story need to give it extra "juice"?
You referred to the GM as a he, you misogynist heretic. I'ma pile more wood on that fire now. 'Scuse me while I get my gasoline can.
The GM is usually the one that keeps track of all the ephemera in play in a game: characters (both player and non, protagonists and antagonists), conflicts, locations, you name it. The GM is usually the one who spends the most time reflecting on this material and considering what might come next. And, in my assessment, although it's not necessarily the GM's job to provide plot twists and surprises, it's occasionally the GM's job to provide material that challenges the players in a way they didn't plan for. The GM's position of being a part of the group but apart from it makes that possible.
None of which is to say that I don't believe in collaborating with players at the highest level. I think that's important, especially early in the formative stage of the game, but also as an ongoing thing. There should always be discussions going on about what could and should happen to the characters next, and the GM should listen carefully to what the players say about that. Most of the time, he should provide exactly what they are looking for.
Joe McDaldno, the writer of the excellent indie game Monsterhearts, described one of the GM's responsibilities thus: Be a fan of the player characters. I think that's an excellent piece of advice. There should be affection and a deep connection between the GM and the PCs. He should always be making an effort to make them "look good on screen" and feature their stories in an interesting and important way.
I enjoy emergent play, but sometimes feel it's too undirected and laconic for our style of game. (Highly structured games like Fiasco mitigate this with built-in twists and mechanisms to keep tension high. In my games, it's the GM who takes the position of being the living Tilt table.) To create drama, both the GM and the players have to push, and maybe the GM has to push the hardest to make sure the player characters stay motivated.
The last thing I should say is that I am also a strong believer in playing shorter games (6-10 sessions) with a definite ending point. I'll probably write about this in more detail at some point, but part of the reason for that is that I'm an older gamer without an infinite amount of time to wait for a game to unfold. Also, I have found that my players are the happiest when I wrap up a game and they have a satisfying sense of closure about it, even if every element isn't entirely resolved (the way sometimes a novel will leave a few things hanging).
Running shorter games means structure. Things have to happen, and happen fast. You need to hit the ground running and push the PCs hard to get to that finish line. You need to push conflicts and reveal secrets and manage all the disparate elements of story quick, quick, quick.
I guess what I'm arguing for is that -- contrary to the common notion that old style GMs want to be authors writing a novel (a notion which I find, frankly, offensive) -- I think that strong GMs are closer to a director in the theatre. The guy who knows the material better than anyone, sitting in the front row night after night, watching the rehearsals, coaxing out nuance and smoothing off the rough edges. The guy (or gal) who loves this material and wants the cast to look good and get applause and leave the stage bursting with the energy the audience has given them, dying to trade stories about it at the pub over a couple of pints.
And if that makes me Old School, or old fashioned, I can live with that. We are all the sum of the gaming baggage we carry with us, it's true, but I don't think that means we need to live our lives in fear of the Douchey GM.
We just have to remember to Not Be That Guy.