Facebook is currently trying to register the word "Face" as a trademark, that they took over from a UK company CIS Internet Limited, which operated a site Faceparty.com. However, at least one person is objecting to this trademark: Aaron Greenspan, Mark Zuckerberg's classmate at Harvard who laid a claim to helping create Facebook, which he later settled.
Greenspan now has his own company Think Computer, which's behind mobile payments app called FaceCash. If Facebook gets the trademark for the word "Face," that could spell trouble for FaceCash. "The possible registration has implications for my company, so I've decided to ask USPTO for an extension of time to oppose it."
Although Greenspan owns the trademark to "FaceCash", he wants to protect his ability to use the word "face" in future products.