My resume was submitted by an employee. I got a call from recruiter next day, she was nice and explained me the process, then scheduled me for phone interview within same week. She was nice enough to provide some interview tips, so I had chance to review some topics. I think fb recruiters are totally on your side.
The phone interviewer was a very nice guy, he was definitely not a recent graduate like some other poster complained, he talked about the pre-internet boom days, so I think he has least 15 years experience.
The phone screen took 45 mins.
First 10-15 mins, he asked about my background and why it's a good match for the position, why I want to work in FB.
Then I was asked to coding question to "find minimum depth of a binary search tree". It was not a hard question, any average coder could do it within 15 mins.
I wrote the code with no hint or help from him. During the coding, he was mostly quite, at one point, he pointed out a possible bug which I fixed instantly. At the end, I was trying to optimize the code, he said the code would work, no need to optimize it further. Then he let me ask questions about FB about 15 mins.
After the interview, I compiled the code and it really worked, didn't even have a single compile error.
Next day, I received a rejection letter from the recruiter with no details.
So trick is, writing the code is not enough, but your code must be very close the most optimized version known and you should be able to write 'close to perfect' code in minimum time.
I googled for similar algorithms and found out my solution was well above the average, but not the best one. I guess they expect you to write something very close to best available code possible can be written, so they single out best coders.
So 'move fast, break things'..