Applied through an internal referral. Had a call with a recruiter who then set up a video interview with a member on the team I was interviewing with.
Interview had one case study question. Make sure to have a strong foundation of product and project management and understanding metrics. There were also lots of behavioral questions which were weaved into conversation.
Not too difficult of an interview, no tricks, but if your new on the job market, I would recommend having several practice interviews prior to your Facebook interview. The process is very thorough and they ask very specific questions.
Interviewer was friendly, but was not able to answer ANY of my questions. May not be a reflection of the company, but of the team.