How to end online harassment

Social networks need to become "walled gardens" again.
The conventional wisdom is that, when it comes to social platforms, open is good and closed is bad.
Facebook used to be slammed as a walled garden. But after Google+ came out in 2011 as a social site with public posts that you could link to and find from ordinary search, Facebook followed suit, and Facebook-as-a-walled-garden was no more. Now Facebook is mostly open (albeit with a flawed real-names policy and proprietary formats like Facebo