Jan Koum toiled at Yahoo for nearly ten years. His attempt to get a job at Facebook was turned down. Jan developed WhatsApp. The number of users quickly surged to hundreds of millions. This time Facebook bought his firm for $19 billion – the most expensive acquisition ever for a venture-backed startup. Jan signed the deal papers at the site of the social-services office where he once stood in line to collect food stamps. This only happens in the US!