James:

Yes, there is a burden on the players. Their burden is to communicate their desires so the GM is not guessing (and their communication may effectively be "We want you to lay the rails for us to follow to the next dungeon").

You point out everyone needs to be on the same page, which is absolutely right, which is why understanding creative agenda is so important.

In my just finished D20 Arcana Evolved campaign, pretty clear railroad tracks led from one adventure to the next, but really the only time I tried to guide things within the adventure was when I had incomplete prep (and I don't think anyone has ever minded the "Dungeon Under Construction" signs [which back in the days we used to actually make explicit - what a refreshing communication if you think about it]).

When I think back to the decision points I presented, there were things like "Where to next?" (when the PCs were in the middle of a "dungeon") or "Do you want to take a boat or walk to XYZ?"

If you've communicated well on the goals of the game, you can even offer the players the opportunity to go on the next adventure, because everyone knows that the answer is of course yes.

And that fails mightly when the players are not all on the same page, as happened with my previous D20 Arcana Unearthed game - twice. I presented an adventure opportunity, and players stonewalled because they were no longer on board. What miserable game sessions those were. Then there was the new player who thought it would be funny to try and sabotage the adventure (who admitted later that he liked to do that to new groups to "test" them of something).

I should note that all of this is all true for simulationism also. Since the game isn't a perfect simulation of real life or some fantasy, there must always be constraints.

Always the key is to understand what are the decision points for your particular game. The GNS mode indicates the type of decision points, but does not indicate the specific decision points (you could have a gamist game where the wilderness has specific encounter tables, and specific areas are at different danger levels etc. and the PCs can be free to go anywhere they want, so "where do you go next?" could be a functional question. But you still don't ask the open ended "What do you do now?"

Chris:

On fun having to involve squeezing water from rocks...

I've been noticing this attitude in lots of places (the place I actually observe it most is in my religion). It seems like people have an attitude that if they had to go through torture to get something, everyone else who follows also has to. I think this attitude is responsible for the number of players who think newcommers to a D&D game should roll up 1st level characters (I've still noted that attitude with D20 gamers - though it's getting less prevalent). I see it when people think D&D should still be about figuring out what the heck an orc actually is capable of (nothing wrong with having some surprise monsters up your sleeve, but guess the monster's abilities isn't really fun anymore, and I'm not sure it ever was all that much fun).

You are probably also right that sometimes it just stems from not being able to identify and communicate what is fun for each person, and mistaken feelings that everyone must be able to have fun even if they perhaps have different ideas of fun.

Frank