Hypersmurf
Moderatarrrrh...
I think the key is: the DMG is for the DM, the PHB for the players. The player shouldn't assume that he can change the rules. But the DM can have this power, and the responsibility. I suppose they should have stressed more that the DM and the players have to talk with each other.
Sometimes, the DM may only need to have an explicit talk with one player.
He might tell the table "This is a game of high adventure and cinematic action", but that could mean all sorts of things.
But if he's talked in more detail with one player about the sort of stunts he wants to encourage, that player can lead by example. If, in the first combat, that player says "I step onto the bannister and leap for the chandelier, sliding down the support rope with one hand while pulling my battleaxe free with the other, and deliver a smashing blow to the goblin leader as I land on the ground floor... whirling in place, I draw the shortsword with my off-hand and ram it into the shaman beside him..."
... it might just be another way of saying "I take a move action to jump off the staircase and move to this square, a free action to draw my weapons with the Quick Draw feat, and a standard action to use Twin Strike". But it also gives the DM a chance to say "Okay - give me an Acrobatics check. If you make a DC 20, you'll have Combat Advantage and you can Push the leader 1 square, if you like."
And whether the DM gives a 'style bonus' or not, when he says "Cool - give me a roll!", it lets the other players see that count-squares-and-use-Power-number-7 is not all they're limited to at this DM's table.
-Hyp.