I was first contacted by an internal recruiter through LinkedIn. We setup an initial call so I could learn more about the opportunity. After I expressed some interest, they setup three phone interviews with their Growth, Engagement and Mobile team. The first interviewer asked a couple of logic puzzles, case questions on how to grow Facebook and how I would go about executing an A/B test. The second interview was a technical interview -- a couple of basic SQL questions. The last interview was a behavioral interview. Afterwards, I received feedback that they would like to invite me for an on-site interview at their HQ. There was some miscommunications with my travel arrangements, but other than some minor snafus, FB took care of everything.
At their HQ, I had 6 interviews with various managers and the head of the Growth team. Many of them revolved around how I would grow adoption of various FB products, their userbase, SQL questions, behavioral-type questions and questions about my past projects. It was not a difficult interview process, but I got the sense they were looking for a particular fit -- someone who was passionate about data, marketing, and could communicate big ideas to grow Facebook. They mentioned they were risk averse when hiring candidates -- they'd rather turn down a good candidate over hiring a false positive.
The campus was lovely and everybody was very friendly towards me. Overall, it was a pleasant experience and if I have another opportunity to interview there, I may do so in the future.