WeirdFacebook

Facebook is now so ubiquitous and dominant that other, alt. subcultures : artistic etc. are evaporating and the remainders are reforming in "dark", "underground" or "alt" parts of Facebook.

http://beststoriesonline.com/science/2015/10/01/Weird-Facebook-Normie-Facebook.html

Obviously these people are misguided. There is no "underground" or "hidden" Facebook. Everything is equally visible to the SysOps.