WhatsApp says that sharing this information means Facebook can offer better friend suggestions by mapping users’ social connections across the two services, and deliver more relevant ads on the social network. Additional analytics data from WhatsApp will also be shared to track usage metrics and fight spam.
WhatsApp reiterated that WhatsApp itself will not show ads, that your conversations are end to end encrypted meaning only you and the person you are talking to is privy to it and not even WhatsApp and Facebook, and that your number will not be handed over to advertisers.
For now, these changes are opt-in, meaning you will be asked to share your account info, and you can choose not to. The option will appear as a popup to users once it starts rolling out.
How to opt out of sharing data for Facebook ad targeting
WhatsApp details two ways to opt out of sharing data for Facebook ad targeting on its blog here.
If you’ve already accepted the new T&Cs without unchecking the box to share your information with Facebook WhatsApp is also offering a thirty-day window to make the same choice — via the settings page in the app.
To exercise your opt out in this scenario you need to go to Settings > Account > Share my account info in the app and uncheck the box/toggle the control displayed there. And do so within the thirty-day window. Presumably, after that, even this partial opt out will expire.