I think that Zynga's major problem is a about changing markets: Zynga grew rich making clones of other games and cleverly using web-based-social-promotion via Facebook to advertise them cheaply. But now they face the same problem that Facebook itself faces - that more users are now mobile based than web-based - combined with the fact that much bigger companies are now not only licencing/cloning games but also combining them with their existing IP which has a much bigger draw for users because of the combined marketing clout behind it.

For example:

* Disney/Pixar now have two top free to play apps based on combining Temple Run with their existing IP. These games not only follow a proven winning formula, but they also piggy back on the movies marketing budgets to promote the games (to a much larger extent that Zynga could afford)

* Universal Pictures has cloned Temple Run Zynga style (but with much more original flair) to make their Despicable Me app game. Like Disney their massive film marketing budget drives the games success, and rather than users having to "warm up" to new characters, the lovable minions are already there for instant recognition/gratification.

* Rovio has made great strides making their original IP (Angry Birds) worthy of Disney level acclaim, but they've also heavily co-branded (via advertising and Angry Birds Star Wars) in order to increase profits.