I realize that Facebook gets enormous amounts of traffic, and so requires the resources for scaling/high availability and all that. But how in the world have they gone through most of $500 million? What the hell are they doing over there?
I'm not sure what facebook has done, or whether this should really be what the focus on, to be honest.
I remember a thread here in HN asking how much time would you need to build a site like Hacker News. Lots of people said something like "a week, top". pg said something like "one year".