Over the past few years, when I have had the opportunity to take part in role-playing games, I have usually done so as the game master--the person who serves as referee for the game and who does the work of developing the basic storyline to follow. The pattern has held true with the game I am currently poised to play; I am running the thing, and so I am tasked with developing the story in as much detail as I can. (I cannot do all of it, of course. Part of the point of the exercise is that the storytelling is collaborative. Daniel Mackay's The Fantasy Role-Playing Game: A New Performing Art discusses the idea in detail.)
As I have begun to do so, I have found that the chapters I write (and I am structuring the overall story--the campaign--much as a prose romance, with books and chapters) have ended up hinging on a single choice, from which players can reasonably follow one of two paths. (There are always other options, like trying to kill everybody in the room. Given the setting, it is not likely to go well; there are safeguards against that sort of thing.) I have tended to call them the Greater and Lesser Paths; the Greater Path tends toward the heroic and selfless, the Lesser toward the villainous and self-interested. And I find that I have been writing the Lesser Path in each chapter before the Greater.
Surely it says something about me that I find it easier to begin by thinking about what will happen when the plan goes wrong than I do about the plan itself. My beloved wife, who is well acquainted with my habits (and encourages some of them), posits that it is my long experience as a game master that tells me to do this. The plan will always go wrong, the players will always do something unexpected and different than the main story calls for, and railroading--forcing players to go along with the pre-determined plot--is almost universally regarded as bad. (All choices might return to a single thread, but there has to be the element of choice involved. I am sure there are studies of this; I would like to see them, so if you know of any, please let me know about them.) I try to be a good game master, so I have to avoid the railroad, and so I have to have the contingencies worked out.
I wonder, though, if it instead speaks to a broader pessimism about the world. I do not (usually) have stupid people at my table; my players are usually very aware of things and of the potential consequences of their actions. Their characters are built with the information in mind that I provide them, and I offer a lot of background knowledge at the asking. I ought to be able to trust them to make the right choice ("right" determined by the milieu; stories happen in contexts), yet I work as though I do not. That I do says more of me than of them, and none of it good.