I was approached by a Facebook recruiter over email, I had no prior relationship. Technical interview via video, followed by an on-site. The whole process took about 5 months. Recruiter contact, call within a few weeks, video screen within a week or two of that, then a long delay of 6-7 weeks waiting for an on-site slot, ~3 weeks after receiving an offer to finish the process with other companies.
The technical interview was very by-the-book and focused on hypothetical scenarios. I don't think I was asked a single question about my own experience and background (although I worked bits of this in via my answers). I'm normally able to establish a good rapport in interviews – as a researcher this is part of my job – but my interviewer seemed to have a very strict process or else had places to be. This made it hard to gauge my performance, but I got a positive response within a few days.
Onsite began with a research presentation based on a prompt they gave me 1 week before the onsite – a hypothetical research scenario, NOT the standard job talk. I'm a mixed methods researcher but have been qualitatively focused for a few years now, so I was concerned about detailed quant questions and did a lot of review. I thought I'd need to be able to talk about sums of squares, maybe write out how an ANOVA worked. I didn't get any questions about this. A few questions about my survey methodology... I mentioned using Cronbach's alpha and that was it.
Across both interviews, Facebook was very focused on overseas research and emerging markets. I have no experience in this area and haven't worked with a research vendor and was not expecting these questions. I was honest about my lack of experience here, as well as my interest in the area. A key point my recruiter made which I think served me well was being honest about my skills: where I was an expert, where I had real experience, and where I would be learning new skills.
Facebook made a tremendous positive impression on me during the onsite. It absolutely feels like a smaller, more vibrant company than it should. Everyone I met with was excited about what they were doing and excited to talk to me as a potential colleague.
I got a positive response a few days later, followed by an extremely competitive first offer. I ended up accepting an offer at a different company where I wouldn't have to relocate, but it was a far harder decision than I anticipated.