Fakebook (Facebook ads getting engagement from fake accounts?).

[gm66]

https://www.theregister.co.uk/2019/01/14/facebook_lookalike_audience/

[rcjordan]

The problem turned out to be a checkbox that allowed ads on third-party sites. Facebook apparently has it checked by default. Over the past five years, Fou explained, there's been a shift in where Facebook shows ads, from Facebook.com to third-party sites that include Facebook ad code.

Once he unchecked it, said Fou, his traffic plummeted but his sales went back up – proof at least that digital advertising can work.

Facebook's Lookalike Audience perhaps taps into dubious third-party websites and accounts that exist to profit from ad fraud.