Well I was thinking, our free form nature is awesome, but may leave the progression of the world itself a bit wanting. So I was thinking that maybe once or twice a year we have a big "world event" adventure that will affect the whole of Pax, and will move the story of the world forward, wherever forward may be.
For instance, say there was a massive zombie outbreak somewhere, that had gotten to such proportions that it was threatening to wipe out an entire country. Any players involved (and hopefully it would be most of them) would have to find a way to either contain or wipe out the threat before it spread. Either the players involved will be big damned heroes or the world is suddenly in a zombie apocalypse that they failed to stop!
Now that's an extreme example but you get the idea.
I imagine the best way to run them would be to have the thread creator primarily run the thread, with help from one or two other people to keep the thing going. That way there shouldn't be too much waiting around.
I would also imagine world events would have to be run by Tav first, or solely posted by him. It's his world after all.

Finally they should be of a nature where any unfinished, smaller RPs can wrap up or even in a way that will allow others to continue if you don't feel like taking part in world plot!
Any thoughts?