This article from The Intercept has been doing the rounds recently. It follows a case lodged by Investor Village, a small financial news message board, against Facebook. The case alleges that Facebook is knowingly mis-selling advertisers on its ad targeting capabilities.
The original complaint, which you can find here, cites internal Facebook emails in which employees describe Facebook’s ad targeting as “crap” and “abysmal”.
The most damning line, taken from an internal Facebook email, is: