Rogue Agent - what difference does it make whether or not you are pre-generating plot?
Well, as you said yourself, it's incredibly difficult to prep the branching structure necessary to deal with divergent player choices if you're trying to pregenerate those plots. This leaves you with two options:
(1) Don't pregenerate plot.
(2) Negate player choices.
Negating player choices has a few consequences:
(1) It negates the defining point of playing a roleplaying game. Roleplaying is, after all, the process of making choices as if you were your character. If you negate those choices, you are negating the very process of roleplaying. (The open question, of course, is whether or not the benefits you're theoretically accruing from negating choices outweighs the penalties.)
(2) For similar reasons, you are negating the group creativity of the table. If you can't figure out why that's a bad idea, I can't help you.
(3) It reduces the spontaneity of the game experience. This is usually noticeable by the players (even when GMs fool themselves into thinking the players haven't noticed); it is always known to the GM.
Some people have effectively zero tolerance for this sort of degradation of the roleplaying experience. Other people have a very high tolerance for it, particularly if it brings with it other benefits that they value. But there is a clear and distinct difference of experience.
If you have honestly never experienced a non-railroaded experience while playing an RPG and are honestly incapable of imagining what that would be like, I feel a little sad for you.
To me, the level of sophistry that people are willing to engage in to avoid saying, "RPG's are collaborative story telling games" is amazing.
You have an unfortunate tendency of talking to the crowd instead of actually talking to individuals. This is not a habit conducive to positive interactions on a public forum.
With that being said, my personal agreement or disagreement with your statement would depend largely on your definitions of "collaborative", "story telling", and/or "story telling game".
This may, or may not, have anything to do with what I'm discussing.
Again, the fact that no one, not one single person, not even the most ardent, "MY GAME HAS NOT PLOT" pundit can give a single, solitary example of play that doesn't generate a story proves my point. EVERY single RPG out there does exactly the same thing - generates a story through the group effort of play.
Consider two games of Chess.
(1) For the first game, the rules include a list of moves. You and your opponent must make the moves on the list in the sequence they're listed. Other moves are not allowed.
(2) For the second game, you're simply playing Chess. You and your opponent can take any moves you want (within the normal rules of the game).
At the end of both games, you have a list of moves. You claim, therefore, that the games are identical. The "my game doesn't have a pregenerated plot" pundits, OTOH, are pointing out that the games are significantly different.