>a walled garden with omnipresent surveillance and advertising
So... a shopping mall? A school? Any corporate job? A walk through downtown? "In-network" minutes and long distance charges on your phone? Religious institutions?
Whatever Facebook is doing wrong for society, they are standing on the backs of giants. Walled garden or not, surveillance or not, advertising or not, people have never been as free to socialize as they are today. If there is something negative on your Facebook feed, you are solely responsible for it being there. It takes two clicks to make it go away forever.