Standard recruiter phone screen, followed by a take-home assignment. Classic case of "this should take you 4-8 hours", when in reality you could spend and entire weekend on the problem and not have a satisfactory solution. The project was to design, code, and test a listing recommender system for the Airbnb homepage. I was concurrently interviewing with a bunch of other companies and didn't have time to complete the project, despite finding the problem very interesting. They provided no feedback about the work I had put together; just a simple rejection email.
All in all, I actually think their interview process is quite disrespectful to candidates. It demands far too much time. The take home project could easily take 50+ hours to complete satisfactorily. Then, supposing you even make it past that point, there are two full days of onsite interviews. In retrospect, I should have declined and not wasted the time I could have spent better preparing for other interviews.