It is my understanding that Aristotle believed one shouldn't work too many hours in the day (I am currently having a hard time finding any references on this, sorry). He (or maybe this was just the culture of his time) believed this is because he placed quite a bit of value on social and political obligations outside of one's work.
Given this, what would Aristotle think about Facebook? Facebook is where many people do most of their socializing these days, and there is a lot of political discussion and news. However, the well-known downside of Facebook is that it promotes a shortened attention span, shallow relationships with less face-to-face time, and excessive amounts of time spent on useless things (cat videos and memes?), among other things.