- the introduction of replays in Halo 3 (which worked the same way - by saving the data of the entire session, one could freely move the camera around the entire map and observe any part of the game at any point in time)

- Super Meat Boy's level-end combined replays (which replayed all of the user's attempts simultaneously, creating a pretty amusing sort of "heatmap" effect)

I think this will eventually become standard for games where replays would be valuable or fun to watch. But I'm not sure about actually rendering live games server-side until we're at a point where input latency is unnoticeable.