This is just a relic of the pre-IPO days when Google kept their infrastructure secret because they didn't want anyone being able to guess how big search was. B

This is just a relic of the pre-IPO days when Google kept their infrastructure secret because they didn't want anyone being able to guess how big search was. Beyond that, Google does a lot of things to run their data centers cheaply - things like keeping a higher ambient temperature (at a cost of higher hardware failure rate), the physical arrangement of servers, etc.