(facebook.com)

Zynga mentioned Facebook 204 times in its S-1 filing. Zynga's fortune is Facebook's fortune, so we wondered, what keeps the game maker up at night? Zynga had plenty of concerns about its dependency on Facebook: terms of service changes, changes to the credits policy, changes to the way it can communicate with Facebook users, and fear of being booted from the platform.

Of course, the ultimate worst case scenario: Zynga fails if Facebook fails. According to Zynga, there are only two serious threats to Facebook long term and across the world:

1. Companies and governmental agencies could decide to block access to Facebook or the Internet.

2. Facebook could lose its market position or "otherwise fall out of favor with Internet users."

So basically, the Chinese attitude and the MySpace effect.