Fiction-generating responsibilities

Maybe this is clear in the book and I just zoned over part of it on my read-through.  We started play with just a couple hours available and generated characters and the MC asked some questions.  And in the intervening time, we've done some fiction-building on our local forum.  And there is some concern on the part of the MC that we (players) are taking a too-active role in fiction-generation.  (I hope that's a fair way to paraphrase concerns expressed over several bits of dialog.)

So, it's the MC's job to make Apocalypse World seem real.  And to barf forth apocalyptica.  What happens when a player barfs forth?

What if I, as a player, just say that I'm going to the old air-strip to salvage old engine parts, but the air-strip has never been mentioned before and bother's someone's vision of the setting?  What if it's the MC and what if it's not?

The MC's job is to maintain the setting. That means exercising editory over the players' input, yep.

When players disagree, they go to the MC to resolve it.

When this has come up in our games, the player with the new barf (and I just have to say - ick.) leads off with something like "Oh, and can there be an old airstrip out there somewhere? 'Cause I have this idea..." Then the MC can think for a sec and say "Yeah, sure. It's like a day's hike away, and there's these people living there who are a bit protective of their space..." "Cool, 'cause I was thinking that's where my operator was form, so she maybe has connections to different tech than around here."

Of conversely, our MC (Hi Vincent) might have said "Yeah, no. But what have you got in mind, and maybe it's something else out there?" And then the player can explain the gist of the idea - 'my operator has some familiarity with tech that's not well known around here' - and we figure out something that works with the player's new input and the MC's editory control.

Yeah, and you can always just keep it to MC questions. So you just have traditional, GM only setting generation, except that the MC is asking all these loaded questions.