[quote=Brovo]
A good GM sets up the stage for the actors, he doesn't hand them scripts. On the flip side, a good player knows to take into account their environment, and set up a character that makes sense for the stage upon which they stand.It's a symbiotic relationship when it works, parasitic when it's only half-functional, and destructive when neither side functions.
[/quote]

Couldn't agree with this more. Dervs' anecdote about a player killing the NPC, too. It requires a lot of trust between the GM and the players to allow for that relationship in forming the story together, and it requires both sides to have a good sense for the story, the characters, and the setting - which is why, perhaps, it's rare to see it done well. When it can be achieved, however, it makes for a much more enjoyable experience - a team effort, a collaborative one, in the spirit of roleplaying itself.