One of the things Snowden had said in a very early interview (something that was denied by officials and called into question by pundits) was that he could sit at his desk in his role, could wiretap anyone and have full access to their web and phone data. 

Welp, one of the files that’s just been leaked is the training documentation for that system. They do give the examples of Facebook, Gmail, etc. It contains screenshots for how to search for keywords through user email storage, Facebook posts, and according to the training material itself, “nearly everything a typical user does on the internet”.