Excellent people, soulless company incentive structure
Pros
Facebook's hiring process tends to find people who are at least good, but often excellent, communicators. Technical skill is a given (and yes, if you got in, that is taken for granted -- stop thinking you're not good enough ;) ), but what astonished me was the way that entire teams worked together in a meta way to improve their dynamics.
Cons
It wasn't always sunshine and rainbows -- expectations are clear and intense, and when you're falling behind, it's incredibly stressful. Furthermore, the entire company is beholden to the ads department for funding, and that department alone is responsible for an unbelievable amount of social and psychological problems in our modern world. Therefore, any work you do feels like you're chipping away at the integrity of the world and of yourself (unless you're one of the lucky few who work on teams dedicated to addressing the systemic issues big tech causes).