I interviewed for a data science position on a smaller team at FB (not the core analytics team). Over a 6-week period, I had a couple of phone screens with recruiters, a technical pair programming interview, and a 5-hour on-site with about 5 different people. The day after the on-site, I got an email from the recruiter saying I did very well, but the team had just gotten word that their "business need had changed" and they would not be hiring for the role. They did not even apologize for wasting my time over the preceding 6 weeks. I'd probably spent more than 40 hours in the interviews and preparing for them. I think it's pretty ridiculous they took me through the whole interview process for a role that never even existed. I feel like FB treats people like dirt because they know that they can and tons of people will still apply. Very disappointing.