WhatsApp Inc.'s system status Twitter Inc. page is displayed on an Apple Inc. iPhone in this arranged photograph taken in Hong Kong, China, on Thursday, Feb. 20, 2014. Facebook, the worlds largest social network, agreed to acquire mobile-messaging startup WhatsApp Inc. for as much as $19 billion in cash and stock, seeking to expand its reach among users on mobile devices. Photographer: Brent Lewin/Bloomberg via Getty Images
