Three 45-minute phone interviews. A positive review from each qualified me for the next stage.

First interview was a basic technical one with their recruiter, covering topics such as port numbers, subnet math, and Linux commands.

Second was a Collabedit programming interview. An engineer had me build a performance monitoring script, adding more features and improving efficiency as we went.

Third was a systems interview, with heavy operating systems theory involved. This engineer's confessed style was improvisational, probing areas of knowledge my previous answers had laid claim to. It helped to know enough systems material and to be interested enough in it to make the conversation span the whole interview time.

I passed the third phone interview, so Facebook flew me to their campus for a day of on-site interviews. I had to sign an NDA covering my experiences on that day. What I can say is that I thought it went at least as well as my phone interviews, yet I got a rejection email a week later.

No particular question strikes a chord.