Exclusive: The Rags-To-Riches Tale Of How Jan Koum Built WhatsApp Into Facebook's New $19 Billion Baby

Jan Koum picked a meaningful spot to sign the $19 billion deal to sell his company WhatsApp to Facebook earlier today. Koum, cofounder Brian Acton and venture capitalist Jim Goetz of Sequoia drove a few blocks from WhatsApp’s discreet headquarters in Mountain View to a disused white building across …