Zynga is facing a lawsuit by another social games company called Agincourt. According to the
Sun Herald, Agincourt "
Owns foundational patents that claim priority back to 1996 and cover the processes for credits-based online gaming and a prize redemption system based on the outcome of game play."
In addition to YoVille, Agincourt named most of Zynga's popular games like FarmVille, FrontierVille, CityVille...
Zynga hasn't commented yet.