Existing users who accept the updated policy will have an additional 30 days to opt out of sharing their account information with Facebook by going to Settings > Account.
Regardless of what you choose though WhatsApp will be able to share the phone number you signed up with, when and how often you use the service with Facebook companies. WhatsApp says it will use this information for "things like understanding services use, securing systems, and fighting spam and abuse across services."
WhatsApp frames the policy changes as good for the user: "By connecting your phone number with Facebook's systems, Facebook can offer better friend suggestions and show you more relevant ads if you have an account with them." Yay, better ads!
“We won’t post or share your WhatsApp number with others," the post continues, "including on Facebook, and we still won't sell, share, or give your phone number to advertisers.”
Facebook currently makes more than $5 billion in advertising revenue per quarter.
WhatsApp still has end-to-end encryption as standard, meaning messages aren't stored on servers, so neither WhatsApp or its parent company Facebook can read your messages, even if they want to.
As WhatsApp says: "Even as we coordinate more with Facebook in the months ahead, your encrypted messages stay private and no one else can read them. Not WhatsApp, not Facebook, nor anyone else."
With these changes WhatsApp is laying down the building blocks for monetising the service without using advertising, with a blog post saying the move forms "part of our plans to test ways for people to communicate with businesses in the months ahead," more than a little reminiscent of Facebook's recent experimentation with chatbots for brands.
Following the Facebook acquisition in 2014 Mark Zuckerberg said he wouldn't serve ads on WhatsApp, stating that it is not the “right way to monetise messaging”. WhatsApp CEO Jan Koum also stated in a blog post at the time that there would have been "no partnership between our two companies if we had to compromise on the core principles that will always define our company, our vision and our product.”
The company has reiterated on this promise today, saying it will still give you "an experience without third-party banner ads and spam," however it is also looking to give businesses a direct line to you via your favourite messaging app, which sounds more intrusive.
WhatsApp gives two examples of how businesses could get in touch with you on the platform: "Whether it's hearing from your bank about a potentially fraudulent transaction, or getting notified by an airline about a delayed flight."
These uses run the gamut from potentially very useful, like your bank notifying you if your account has been compromised, to intrusive and annoying, or 'product and service updates, and marketing'.
How the company will charge businesses for this level of access to its 400 million plus users is yet to be seen, but business accounts are due to begin pilots over the next few months.
But the user will have a say in these interactions, with the new policy stating: "We do not want you to have a spammy experience; as with all of your messages, you can manage these communications."
WhatsApp has come a long way since Jan Koum created the extremely popular messaging app in 2009, before selling to Facebook for $19 billion five years later.
Ukrainian born developer Jan Koum built WhatsApp with privacy in mind. Growing up in the secret police state of Soviet Ukraine, so the story goes, formed Koum's commitment to private communications as he developed the super-popular app.
Under his stewardship the service was never tempted to harvest user's personal data for commercial gain, trust was more important. The service would access your phone number and your contacts, and asked for location services, but little else.
WhatsApp hasn't moved away from these core principles just yet, but once you are in the gravitational pull of an advertising behemoth like Facebook, concessions might need to be made.