WhatsApp (Meta)

Jan Koum and Brian Acton both worked at Yahoo for nine years before leaving in 2007. In 2009, both applied for jobs at Facebook. Both were rejected. Acton later tweeted about the rejection: "Facebook turned me down. It was a great opportunity to connect with some fantastic people. Looking forward to life's next adventure." Five years later, Facebook paid $19 billion to acquire the company they had built.

Jan Koum founded WhatsApp in January 2009, initially as a simple app to display status updates next to contacts in a phone's address book — "Jan is at the gym," "Jan is on a call." When Apple launched push notifications, users began using the status field to send messages. Koum realised he had accidentally built a messaging app and leaned into it.

WhatsApp grew to 200 million users without spending a dollar on marketing or advertising. Koum had a deep personal aversion to advertising — he had grown up in Soviet Ukraine where surveillance was normalised and believed strongly in communication privacy. WhatsApp's business model was a $1 annual subscription fee, later dropped entirely. The product spread purely by word of mouth.

Facebook acquired WhatsApp in February 2014 for $19 billion — the largest acquisition of a venture-backed company in history. WhatsApp had 55 employees at the time of the sale, making each employee worth approximately $345 million on paper. Koum and Acton joined Facebook's board. Zuckerberg promised that WhatsApp would remain independent and that its privacy principles would be preserved.

Brian Acton left WhatsApp in September 2017, forfeiting approximately $850 million in unvested stock. Jan Koum left in April 2018, also forfeiting unvested stock worth hundreds of millions of dollars. Both departures were linked to pressure from Facebook to monetise WhatsApp through advertising and to share user data with Facebook's ad targeting systems — the exact thing both founders had built WhatsApp to avoid. Acton later tweeted: "It is time. #deletefacebook."