Last week I was representing Bromium at the Hacker News London event, and there was an excellent talk by Philip Su from Facebook's London office. It was about the engineering culture at Facebook and how they have kept it working up to their current 1000 engineers. Whatever you think of Facebook this is a great window into how they have kept the engineering culture thriving and fully operational despite the issues of engineer numbers and the scale of their operations.
Also, Philip Su is a really great speaker.
Philip Su: Site Lead at Facebook - Engineering process and philosophy at Facebook from HN London on Vimeo.