Easy there, Mark Zuckerberg: Social-networking giant Facebook is on a mission to trademark the word "face," thereby preventing any other social-networking sites from using the word in their brand names. Not surprisingly, this decision has been met with some opposition, including protest from one familiar... face. Aaron Greenspan, a former Harvard classmate of Facebook founder Mark Zuckerberg who claimed he stole the concept of Facebook from him—as well as developer of a mobile app called FaceCash—may file a formal opposition to the trademark attempt. "If you search the patent database, there are thousands of marks that contain the word 'face,'" he said. "I understand where Facebook is coming from, but this move has big implications for my company and for others." Facebook has also come out against other sites using the word "book" in their titles, pursuing legal action against Teachbook.com and travel site PlaceBook. According to one trademark lawyer, in the Teachbook case, Zuckerberg's site would have to prove "a likelihood of confusion" between the two sites.