It’s a very unique environment, not easily replicated (nor would their system work for all companies, even if they tried). These are notes gathered from talking with many friends at Facebook about how the company develops and releases software.
This is more or less how we work, though at a much smaller scale. Its a very 'agile' and engineering driven approach and I find little of this surprising. However this peek inside how it works with 1000 Software Engineers and Operations staff is fascinating.