Facebook is also enforcing new terms for its developers: From December on, applications that run on external domains instead of appearing as an iframe inside facebook will be severely restricted in their access to facebook[1]. This move is supposed to force indie developers to move their games to facebook where they can't use AdSense (it's not allowed by facebook) and can only use facebook's own payments system (it's mandatory).

Zynga could have used this 2 year time window to grow an independent social gaming network, but they failed to do so. It was inevitable that this would happen.

[1] https://developers.facebook.com/blog/post/2012/09/05/platfor...