Pascal Zachary get it right, IMHO:

Consider the question of Google’s greatest business secret. Is it the algorithms behind its search tools? Or is it the way it organizes vast clusters of computers around the globe to answer queries so quickly? Perhaps predictably, Google won’t disclose the number of computers deployed in its vast information network (though outsiders speculate that the network has at least 450,000 computers).

I believe that the physical network is Google’s “secret sauce,” its premier competitive advantage. While a brilliant lone wolf can conceive of a dazzling algorithm, only a superwealthy and well-managed organization can run what is arguably the most valuable computer network on the planet. Without the computer network, Google is nothing.

Eric E. Schmidt, Google’s chief executive, appears to agree. Last year he declared, “We believe we get tremendous competitive advantage by essentially building our own infrastructures.”