For Facebook, 2018 ended the way it began — with embarrassing headlines about Mark Zuckerberg’s failure to keep his digital house in order. Twitter had its own issues as well, with significant questions about who it bans and who it does not.

Emily Rooney was joined by Adam Reilly of WGBH News, Joanna Weiss of Experience Magazine, Dan Kennedy of Northeastern University and Callie Crossley of WGBH News.