Keep in mind that most of those 1.86 billion "users" never actually post anything. I forget the exact fraction, but it's very large.
Identifying Facebook users wouldn't prevent these sorts of abuses. You think the police/authorities have any real difficulty identifying a Facebook user who posts a video of themself committing murder? I don't. "Evading arrest" is not part of their agenda, they're just angling for their 15 minutes of fame. That's how sick our culture is.
I think Facebook should (1) stop hosting video content entirely, (2) aggressively filter photos, and (3) impose a delay (of at least 30 minutes) between an update - any update, including pure text or links - being posted and it actually being visible online. I think that would change the psychological dynamic of posting something shocking.