Zynga recently made an amended IPO filing that confirms that Google has invested in the social gaming company. I wrote about that deal in July 2010 and the amended filing confirms it.
The filing also reveals that any game that Zynga builds that includes Facebook integration or Facebook data will be exclusive to Facebook for the duration that the two companies agree to. Zynga must also let Facebook know about new games one week before launching. Facebook can decide which games that Zynga can launch. In a way, Zynga appears to be an outsourced gaming arm for Facebook.