Facebook Chief Executive Mark Zuckerberg attends a keynote presentation event at the Mobile World Congress in Barcelona

Facebook Chief Executive Mark Zuckerberg attends a keynote presentation event at the Mobile World Congress in Barcelona March 2, 2015. Ninety thousand executives, marketers and reporters gather in Barcelona this week for the telecom operators Mobile World Congress, the largest annual trade show for the global wireless industry. REUTERS/Albert Gea (SPAIN - Tags: BUSINESS SCIENCE TECHNOLOGY TELECOMS)