It's been interesting to watch some of Wynn-William's claims be vindicated by recent court decisions about the addictive and manipulative qualities of Meta and Google's products. She left the company in 2017, and along with her many other allegations about Facebook and their executive team, had a good amount of information in the book about the reasoning, rationale, and management decisions that led to allowing advertisers to hyper target "coveted" demographics of tweens and children (among other claims).
Facebook, according to Wynn-Williams, sold advertisers on the fact that they could target young girls who post and then remove selfies from their services in order to market to demographics who were likely experiencing depression and negative feelings about their body image.