Let's face it, the days of tinkering with virtual worlds on Facebook for bored office workers or young mothers connecting to the outside world between kids' naps has peaked. It's just not as fun anymore. Every new game that comes out is just a copy of the last game, and as people care less about what their friends' "Farms" or "Zoos" or "Sororities" look like... the less they're going to tend to their own.
I'm not saying there's no innovation any longer, because there is. The problem really is, Facebook is losing its edge as a personal platform. People may still be using it as a place to passively stay in touch with others, or to publicize their witty thoughts and silly photos. But, as the platform opens up to integrations such as Twitter, YouTube, millions of Fan Pages and Groups, annoying updates from applications like Farmville, Zoo World, Restaurant City, and online ads galore begging for users attention to turn to the right hand pain of the screen, it just doesn't feel personal anymore.
Facebook is turning into an online platform that ENABLES users to socially browse the web - think Facebook Connect for news, ecommerce, blogs, etc.
And Social Gaming isn't dead ... it's just being resurrected in more convenient places like the iPad, the iPhone, the Android.