What you're not mentioning is that it's never a 100% dictatorial process, either. In fact, it's usually a more collaborative decision than you might realize.
I would really appreciate it if you would stop telling me that "I might just realize [such and such]" if I thought your way. First, I do not (in case that was not abundantly clear). Nor do I care to (also, in case that was not abundantly clear). I understand my own gaming style pretty well, thanks. I, at no point, have debated that gaming has collaborative elements - maybe even a majority collaborative process. What I do debate is the extent of that collaboration. I believe that there is a stopping point, a distinct boundry to which collaboration is either paying diminishing returns or is simply not the appropriate tool for the game. We have butted heads before on how much collaboration, GM fiat (your wording, here) etc. is acceptable in gaming.
I do not believe in adbicating or dissipating the authority and responsibility of running the game. My reasons for this, as I pointed out earlier in the thread, are nigh on identicaly to MaxMahem's: the abdication of responsibility by the GM into the hands of the players puts the fate of PCs into a state of surety that marginalizes their efforts in ways that erode the game's challenge, suspension of disbelief and fun. There are ways around this, sure; but I do not prefer those game systems. Further, I consider those systems to work well within themselves. I have tried 'Drama Dice' in games before and the feel of the game was noticibly changed as was my intention. As the GM I looked to other mechanical devices to achieve a certain feel to the game. What I find amusing is that I, rather autocratically I might add, forced a rules set into a game (where these rules really did not belong) to achieve a goal. My players went with it (I guess their aquiessence was a sign of 'collaboration') and everyone had fun (our goal, right?).
In any case, I will be (mostly) bowing out of this nonsense. My position has been stated really very clearly. I have used the term 'organic' (as Max did) countless times amongst my gamers. I strive to create a world that exists with or without the players and will react in an intelligible and real fashion with whatever my players do. To draw on the other thread where Cain and I butted heads - a car does not go Mach 4 without ripping itself apart as physics in my SR games still apply in any situation. These kinds of fundamental laws govern the way that I run games. Once I have enough of them in place, have a bevy of NPCs and locations etc. the PCs are free to run about doing what they do (Generally killing people, breaking or stealing stuff for money. Gotta love SR.) willy nilly. What does happen, though, is that some incredible improv will grow out of the game. Because I understand what the world contains, how it lives and breathes (and my players grow to understand as well) there is a great deal of continuity that grows between events. Once the great wheezing beast is cobbled together I can turn her on and let her run with little interference.