That is damn brilliant. Much more scalable (and I think just much more elegant) than the craziness we came up with.

That said, I think we'll leave this on the back burner until it's an issue. (We're always reminding ourselves to only work on things that are solving problems right now, not problems we're going to have -- when we scale up, when someone wants to do such-and-such.) To quote Patrick McKenzie: "A startup's most likely problem with scaling is that it will have no scaling problems."