"Google is a company that has built a single very large, custom computer. It's running their own cluster operating system. They make their big computer even bigger and faster each month, while lowering the cost of CPU cycles. It's looking more like a general purpose platform than a cluster optimized for a single application.
While competitors are targeting the individual applications Google has deployed, Google is building a massive, general purpose computing platform for web-scale programming.
This computer is running the world's top search engine, a social networking service, a shopping price comparison engine, a new email service, and a local search/yellow pages engine. What will they do next with the world's biggest computer and most advanced operating system?"
More at: The secret source of Google's power