Facebook is back online again.
It appears they switched over to their QA/UAT systems.  It's up and down all over the place, with people reporting missing data and missing posts.  It's not up where I am and still down in large parts of the world.  Switching to QA is usually an act of desperation.
This wasn't an accident or a fluke, but was done on purpose.  Question is who and why.  And whoever did this to production, could much more easily do it to QA.