Reuters: Yahoo has filed a lawsuit in San Jose, California, alleging that Facebook infringes on ten of its patents. Two of the patents mentioned in the suit relate to social networking; the rest relate to advertising, such as ways to prevent click fraud and customize ads. Yahoo is seeking licensing fees.
In response, a Facebook spokesman said, "We're disappointed that Yahoo, a longtime business partner of Facebook and a company that has substantially benefited from its association with Facebook, has decided to resort to litigation."
Facebook has recently filed paperwork indicating its intention to take the company public. Yahoo also also sued Google right before that company went public.