I have had 6 managers in 3 years. Facebook has a lot of reorgs. And I am certain all of this change has hindered my career growth. Even though I have received top reviews I have not been able to achieve a promotion.
Regarding the culture -- Generally everyone is great to work with and good at their job. However, there are a some people who seem unfamiliar with a professional work environment. These people can cause lots of drama and generally seem ungrateful for the tremendous opportunity we have at Facebook.
It can be difficult to deal with all the attacks on the company from the press. When you see so many amazing people working hard to get things right, and the press only focuses on (predominately false) negative articles, it is hard not to get discouraged.