People stand and work on mobile devices, a smartphone, left, and a Apple Inc. iPad whilst framed against a wall bearing Facebook Inc.s 'Thumbs Up' symbol in this arranged photograph in London, U.K., on Wednesday, Dec. 23, 2015. Facebook Inc.s WhatsApp messaging service, with more than 100 million local users, is the most-used app in Brazil, according to an Ibope poll published on Dec. 15. Photographer: Chris Ratcliffe/Bloomberg via Getty Images
