After Facebook bought WhatsApp for way too much money, the company reiterated a promise to its users: It would never allow its service to be used by advertisers to message users. Founder Jan Koum once said,
When we sat down to start our own thing together three years ago we wanted to make something that wasn't just another ad clearinghouse. We wanted to spend our time building a service people wanted to use because it worked and saved them money and made their lives better in a small way. We knew that we could charge people directly if we could do all those things.
We knew we could do what most people aim to do every day: avoid ads.
This is a sharp change in policy for the company, but one that everyone knew was coming. For users whose accounts existed before the change, you will be able to turn off the Facebook sharing option. However, WhatsApp said,
The Facebook family of companies will still receive and use this information for other purposes such as improving infrastructure and delivery systems, understanding how our services or theirs are used, securing systems, and fighting spam, abuse, or infringement activities.
So, checkbox or not, Facebook will know a lot more about you if you use WhatsApp.