https://techcrunch.com/2021/02/18/facebook-knew-for-years-ad-reach-estimates-were-based-on-wrong-data-but-blocked-fixes-over-revenue-impact-per-court-filing/

Some more internal emails Facebook really doesn’t want you to see: Turns out in 2017 COO Sheryl Sandberg had already known for years there were problems with a free ad planning tool the company offers to marketeers to display estimates of how many people campaigns running on its platform may reach, per newly unsealed court documents.

The filing also reveals that a Facebook product manager for the ‘potential reach’ tool warned the company was making revenue it “should never have” off of “wrong data”.