"Once you had your first perfect first-person-shooter mechanic, it became apparent that you could apply it to different time periods in history, to science fiction themes, to fantasy themes, and so on. That's the same thing that's going on here. If you compare farming to first-person shooters, you can now take farming and add social elements and decorating elements and multi-player elements. A bit of genre hybridization is going on and the games are getting a bit broader as that happens."
-Metaplace founder Raph Koster explains to Gamasutra
how casual and social gaming is branching out through games based around everything from chocolate