I thought this would be of interest to some:
http://www.mattcutts.com/blog/indexing-timeline/
Very long post. Here is a snippet.
,----[ Snippet ]
| Fair enough. Some people don't want to read the whole mind-numbingly
| long post while their eyes glaze over. For those people, my short
| summary would be two-fold. First, I believe the crawl/index team
| certainly has enough machines to do its job, and we definitely
| aren't dropping documents because we're "out of space."
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