A woman holds a tablet displaying WhatsApp’s logo in front of the screen with the Facebook logo in this photo illustration taken in Prague February 20, 2014. Facebook Inc’s purchase of fast-growing mobile-messaging start-up WhatsApp for $19 billion (11 billion pounds) stunned the markets but analysts said the deal made strategic sense as it will solidify the social network’s position as a leader in mobile. Picture taken with a zoom burst. REUTERS/David W Cerny (CZECH REPUBLIC – Tags: BUSINESS LOGO SCIENCE TECHNOLOGY BUSINESS TELECOMS)