I doubt that Zynga's decline has anything to do with their flawed mechanics (I'd argue that it's flawed too), and everything with Facebook effectively killing i

I doubt that Zynga's decline has anything to do with their flawed mechanics (I'd argue that it's flawed too), and everything with Facebook effectively killing it (specifically, 'Requests') in feed. There's no feedback loop in there anymore for Zynga's cows.