One of the things I remember from an internship there a few years ago, Facebook does its main "push" of new code to its server farms on Tuesdays around 5pm (i.e. around this time). It would be interesting to read a postmortem on what brought down the most visited site on the world—was it an image staging issue? A latent bug in the product? A badly configured setting? A malicious attack? A network problem? Hopefully Facebook Eng will do a write-up on the root cause!