Before all the bloggers started their own blogs...
Google brought back the index from January 2001 to show how many things have changed in almost 8 years. At that time, Google's index included 1,326,920,000 web pages and it was the most comprehensive index of a search engine.
Google explains that the index from January 2001 is the earliest available. "Well, for various technical reasons that are too boring to go into, earlier versions of our index aren't readily accessible. But we did still want to offer users a chance to search an older index as a way of looking back at web history, and the January 2001 index is the best we can do."