Excerpt from Steve Yegge's blog:

At first it's entirely non-obvious who's responsible for Google's culture of engineering discipline: the design docs, audited code reviews, early design reviews, readability reviews, resisting introduction of new languages, unit testing and code coverage, profiling and performance testing, etc. You know. The whole gamut of processes and tools that quality engineering organizations use to ensure that code is open, readable, documented, and generally non-shoddy work.