More thoughts about this: one of the traditional modes for a campaign is that of traditional tabletop: the GM comes up with a setting and an epic story over however many episodes, with key scenes and a huge climax. The traditional failure mode for this style is railroading - the characters do something unanticipated, and the GM has to get them "back on track". The deeper failure mode is the players losing interest in the GM's story because its not their story; their characters evolve their own stories which pull them somewhere different, rather than to the GM's epic finale. I think we've seen that failure mode in some local campaigns, with players dropping out of final episodes because they don't like where the story is going, and others having to steer hard to stay involved.
One of the tabletop responses to this comes from indie gaming, and its basicly to empower the players to co-create not just the setting, but also the narrative. Instead of exhaustively defining the world and nailing down every chamber-pot, you have a rough sketch, leave gaps, and explicitly ask the players to do it for you. And instead of having a pre-planned story arc, you have a vague initial situation and a few leading questions for the players, who get to make up who the antagonists are and their motivations. We've seen larps which have done this locally as well, notably Kingdom and The World That Is. They've worked well, but they're small. Obviously with bigger games you're going to have problems with prompting everyone, coherence and limited GM attention, but the narrative principle of "play to find out what happens" is the take-away here.
The metaphysics suggestion is good. One of my favourite tabletop rpgs is Ars Magica, a crunchy early '90's game about medieval wizards. One of the reasons I like it is because it explicitly provides a consistent set of rules for magic, letting the players know exactly what they need to do in order to achieve a specific effect and freeing them to be proactive. The GM can then simply present them with problems and let them figure out how to solve them and what consequences they are willing to bear. Its easy to see how this can work in a larp.
I'm not sure what the current crop of campaigns are doing for narrative design. Anyone want to chip in?