What's Facebook building?

THEY'VE GOT SOMETHING TO SHARE: What's Facebook building? We'll know tomorrow morning, when the online behemoth holds a press conference at its Menlo Park HQ. Speculation has understandably been rampant among tech geeks. Some have guessed Mark Zuckerberg's social-networking site is preparing to launch a phone (denied by MZ with enough vehemence to be read as a confirmation by some observers), a new search function, an enhanced blogging feature, an army of robotic assassins, etc. The pressure would appear to be on for Facebook to make an impressive leap; a recent survey, the L.A. Times reports, finds it lagging behind Tumblr in popularity among users between 13 and 25 years of age. (1/14p)