You'd think something like this would have been standardized by now, but it hasn't (not that I know of, anyway.) Perhaps the patent issues surrounding token ring networks make it unattractive
Or maybe the fact that a single malfunctioning device will take down the entire network?
It's certainly not a bad idea, very nice in terms of simplicity, but it isn't exactly robust.
I suspect no one has done it because RS485 has pretty much done the same thing (bus instead of ring, though).
-j