Think a moment of how Facebook works. Members of the social media network can make a post or share an article, reply to it, share it again, comment on it, etc. Who can see the post and those subsequent annotations depends on permissions set by the poster: specific friends, all friends and the public. Those comments and shares can be seen as a sort of commentary.
Barker sees the Facebook model working in the world of legal citation indexes in a few different ways.


