Alleged ex-Zynga employee tells all on Reddit:
 Spying on players. Getting intimate gaming data, their habits, their networks, and how to effectively monetize given X. Another issue was skewing gameplay for the sake of profit, example; I actually resorted to BAD MATH, to make the case for making a feature more fun. At the end of one sprint, a QA dude was complaining about the drop rate of a specific item being absurdly insane, and therefore UnFun. I looked at the code, and tweaked some values, gave it back to QA guy, and fun was restored. Product Manager overrides this, goes for unfun, yet more profitable version.
Not that people didn’t know that Zynga were a bunch of evil buggers…. Here’s the reddit thread.