Later in the book, the China story was a close second. In order to get into China (to "grow") - exec team agreed to host Facebook's servers in China where the government could get access to customer private data, so they could stifle dissent.
Tons of other weird/bad/embarrassing stuff too. The author, a member of the core executive team, was seriously complicit but redeemed herself in my view with this no-holds-barred account of the complete lack of ethics up top.
In general a damning portrait of the executive team as just not giving a shit about anything except for growth and willing to actively participate in dictatorship in order to make it happen.