Castrum - It would appear Nintendo has decided to corner the market on Single-Player games that can optionally become Multiplayer:
Back in 2010, Nintendo filed a patent application for something called a "massively single-playing online game," something whose interactions don't take place in real time and what sounds a little Animal Crossing-ish (above).
According to GameSpot, which found the filing, the MSO(?) would be an environment where players' actions and choices affect the world they and everyone else inhabit. Economic systems are a good example, one Nintendo used in the filing.
I call Patent Trolling.
http://kotaku.com/5830500/nintendo-seeks-to-patent-the-massively-singleplayer-online-game
That actually sounds pretty good, and the kind of thing I'd be interested in. Sometimes I play MMO's merely for the story, or game, and have no intention of interacting with other people.