Facebook Whistleblower Makes Shock Claim About Mark Zuckerberg During Senate Testimony (youtube.com)
They created a ‘chief editor’ in mainland China, who reviewed any post that had over 10k likes, and also could turn off the Facebook service if they wanted, for example on special days, aniversaries, etc, she said.
I don't know about the witness though. She seems fairly purposeful. And she's just one person.
Teenage girls who've recently deleted a selfie (because it showed low self-esteem), and with young mothers there was some metrics to track their negative emotional state, and they used that to target ads.
13-17 is the most valuable ad market.