People come and go. Sometimes, someone who starts with the best of intentions can’t make it past the first session of an ongoing game due to any of the various slings and arrows of life. Sometimes, a friend is in from out of town for the weekend, and you want them to join.
Some games have beautiful design, but at the cost of being rigid in the face of these considerations: Smallville, for example, doesn’t handle people coming and going very well. Nor does Polaris. Both of these are beautiful games, and if you can get a reliable group, are, I imagine, fantastic.
I want to design games that can have the best of both worlds—the cohesion of a storyline where the same characters reliably recur, and the tolerance for real-world exigencies of games that don’t rely on people showing up all the time. One way to do this is to break the character-monogamy attitude. This leads to another problem, at least potentially: a character played by a rotating band of folks can be incoherent, with no consistent characterization or motivation.
So, are there other ways to do this? I hope so.