The messy break-up between the WhatsApp founders and Facebook was recently detailed by The Wall Street Journal.
Facebook bought WhatsApp for US$22 billion in 2014 and the two companies sought to get users onside with an ad campaign which revolved around WhatsApp's slogan of "no ads, no games, no gimmicks".
The message given out was that while Facebook would continue to run advertising on its own pages, WhatsApp would not be touched.
But Facebook's Mark Zuckerberg and his chief operating officer Sheryl Sandberg put pressure on Koum and Acton and finally the two left the company in disgust. In the words of the WSJ, Zuckerberg and Sandberg "“grew impatient for a greater return on the company’s 2014 blockbuster US$22 billion purchase".
In a blog post from June 2012, Koum wrote: "No one wakes up excited to see more advertising, no one goes to sleep thinking about the ads they'll see tomorrow. We know people go to sleep excited about who they chatted with that day (and disappointed about who they didn't).
"We want WhatsApp to be the product that keeps you awake... and that you reach for in the morning. No one jumps up from a nap and runs to see an advertisement.
"Advertising isn't just the disruption of aesthetics, the insults to your intelligence and the interruption of your train of thought. At every company that sells ads, a significant portion of their engineering team spends their day tuning data mining, writing better code to collect all your personal data, upgrading the servers that hold all the data and making sure it's all being logged and collated and sliced and packaged and shipped out...
"And at the end of the day the result of it all is a slightly different advertising banner in your browser or on your mobile screen."
Acton left in September 2017 while Koum quit in April this year. The distaste the pair have for Facebook's business model can be gauged from the fact that Acton gave up about US$900 million to leave while Koum sacrificed US$400 million.
They had to give up these amounts because, while their agreement with Zuckerberg stipulated that they could leave at any time and be paid out in full, the small print said that they would have to sue in order not to lose any money. Apparently, neither could be bothered to do so.
Acton has invested US$50 million in the Signal Foundation, a project to help make private communication accessible and ubiquitous.
The project is run by cryptography expert Moxie Marlinspike, who also runs Open Whisper Systems that develops the Signal protocol and the Signal messaging app that provides secure communications.