An excerpt from - Scan this book - from the NY Times Sunday magazine:
Search engines are transforming our culture because they harness the power of relationships, which is all links really are. There are about 100 billion Web pages, and each page holds, on average, 10 links. That's a trillion electrified connections coursing through the Web. This tangle of relationships is precisely what gives the Web its immense force. The static world of book knowledge is about to be transformed by the same elevation of relationships, as each page in a book discovers other pages and other books. Once text is digital, books seep out of their bindings and weave themselves together. The collective intelligence of a library allows us to see things we can't see in a single, isolated book.