Very interesting article at O'reilly, all about how the Wayback Machine Works » "a book is a megabyte, which is about what it is, and the Library of Congress has 20 million books, that's 20 terabytes. This is 100 terabytes. At that size, this is the largest database ever built. It's larger than Walmart's, American Express', the IRS. It's the largest database ever built. And it's receiving queries [...] at the rate of 200 queries per second." (via EvHead)