WhatsApp co-founder and CEO Jan Koum is leaving the company amid arguments with parent company Facebook over data privacy and the messaging app's business model, according to a report from The Washington Post. Koum, together with his fellow co-founder Brian Acton, sold WhatsApp to Facebook in 2014 for an eye-popping sum of $19 billion, $3 billion of which consisted of Facebook stock granted to both Koum and Acton, who left the company back in September. Koum confirmed his departure in a personal Facebook posttoday.