Facebook is buying the hugely popular WhatsApp for $16 billion according to a filing with the SEC. The purchase, $4 billion in cash plus $12 billion in Facebook shares and potential for an additional $3 billion in employee stock payouts, will see WhatsApp founder Jan Koum joining Facebook's board of directors. WhatsApp Messenger is a hugely popular cross-platform messaging app that allows users to chat with individuals or groups, as well as sending files and pictures back and forth. Back in December, the service bragged that it had 400 million active users, with 100 million of those added in the last four months of 2013. Back in April of 201
