Pros
Probably the most important thing about Facebook is the culture. Engineers are always free to solve problems when they see them. Generally there are no hard deadlines to meet, so you can almost always put something to the side when you think there's something more valuable to do. If you find a bug in somebody else's project, fix it. If you have an idea for a useful feature, make it. We're willing to try anything once. The agility of Facebook is amazing, because all engineers are expected to be able to help out with anything. The org is very loose. And the benefits are fantastic. Free food, laundry, shuttle service from all over the Bay Area, and much more.
Cons
I frequently take a moment to consider what I would want to improve at Facebook, and I never come up with anything. I could see how if you were somebody who really needed structure and direction, you could get frustrated. Facebook strongly encourages engineers to try working on new things every so often so that you're always learning, and also expects autonomy.
