The whole concept behind players getting to control story in RPGs, be it fully-blown Forge games, or in the use of "plot point" type mechanics where the Players can alter some aspect of reality to suit his purposes is that, aside from destroying the whole idea of emulation and a lot of immersion, the basic premise behind the reasoning for such mechanics is completely flawed.
That basic premise would be defined as something like "the game is more fun when I'm in control of what happens to my character"; or put another way "the game is more fun when I'm winning".
In RPGs, that's simply not the case. Being able to ensure, due to mechanics as much as due to whineyness, that your character will never lose is an incredibly boring predicament to find yourself in. It explains why Storygames are mostly all obsessive little micro-games that can only be played for one or two sessions. More than that and they outlive all use.
The moments when players are absolutely at their finest, and enjoying the game the most is not when they're winning, but when interesting things are happening to their characters. And that "interesting" almost always involves great conflicts, drama, and SUFFERING. Being able to wish away any negative results with a plot point or because the GM isn't allowed to say "no" according to the pseudo-intellectualoid game designer completely ruins that possibility of a PC suffering, and therefore evolving, and deepening as a character, and therefore bringing real entertainment to his player.
Its really rare for any player I know, barring a few really immature or boring ones, to go around bragging about how awesome their character was for winning really easily every time because nothing could stop him. All the good stories about awesome things usually involve terrible terrible things happening to a PC, complications and setbacks that were humorous, impressive, shocking, and the difficult process of overcoming them. You want "story", motherfucker? There's story. And saying "I wish that away with a plot point" or "i have narrative control now" is specifically losing out on what really creates great game.
(Originally Posted April 20, 2009)