In-Depth Explanation of Google Indexing Timeline

Matt goes on at some length (about 2,000 words) to explain recent changes to Google crawling and indexing process and the Bigdaddy roll-out earlier this year in his Indexing timeline post in his blog. The comments get even longer, but it is an interesting read which explains in part at least why so very old supplementary records have hung around in the Google database for so long.