Facebook wasn't "build first" in any appreciable sense. The prototype features were outlined in a well received editorial in the Harvard Crimson in December of

Facebook wasn't "build first" in any appreciable sense. The prototype features were outlined in a well received editorial in the Harvard Crimson in December of 2003. There was widespread outcry for the administration to build what Zuckerberg realized he could build faster. Further, there were existing prototypes in house facebooks. Source: user number under 10k