GSC Game World is crowdsourcing S.T.A.L.K.E.R. 2 -- well, a small part of it, anyway. The studio is currently holding a contest in which creative types can submit their quest ideas (up to five) for the impending post-apocalyptic game.
The rules are broken down on Facebook of all places, so go ahead and read up on the fine print. GSC Game World is looking for relatively brief descriptions, not twenty-page fanfics. The names of the contest winners will be included in the game's credits, and the winning quests might be implemented. Might.
Of all the games to do this, S.T.A.L.K.E.R. 2 has got to be one of the safer choices. The community was already coming up with content like this before, and now they have even more motivation to do so, and to do so well.
Design your own S.T.A.L.K.E.R 2 quest [Eurogamer]