When WhatsApp announced on Thursday that it would start sharing data with its corporate parent,Facebook, some of its fans howled that the popular messaging service was betraying long-held promises to protect their privacy. But for the companies, angry users may pose less of a problem than the Federal Trade Commission, which serves as the country’s top privacy regulator.

Recall that in 2014, after Facebook GOOG -0.03% announced it would acquire WhatsApp, the FTC’s Bureau of Consumer Protection sent a stern letter to the companies warning them to honor their promises to consumers or face an investigation into unfair trade practices.

That letter also pointed to specific pledges from the companies including one by Facebook CEO Mark Zuckerberg who insisted that, “We are absolutely not going to change plans around WhatsApp and the way it uses user data.”

The result is that WhatsApp, which has over 1 billion users, will have to tread very carefully as it implements its plan to share information such as phone numbers and analytics data with Facebook. (While WhatsApp users will have an option to block Facebook from using certain data for advertising, they will be unable to block Facebook from linking the accounts internally to get a better picture about who its users are and, possibly, an even better idea about who they know).

For Facebook, the task of carrying out all this in a lawful manner is more challenging still since the company is under a 20-year consent decree related to earlier complaints about its privacy policies:


William McGeveran @BillMcGev

If @facebook & @WhatsApp didn’t consult @FTC before making this privacy policy change, they could be in hot water.https://www.ftc.gov/news-events/press-releases/2012/08/ftc-approves-final-settlement-facebook 



The FTC, as is its custom, declined to comment on how or if it will scrutinize Facebook’s plan to integrate the WhatsApp data.