Google will no longer tell us how many billions of web pages they've indexed, though they do claim to be "more than 3 times larger than any other search engine." John Battelle tells the story over on Searchblog.
Of course, index size is a flawed metric. Most users never get past the first 10 results, and neither Google nor Yahoo! lets you explore beyond the first 1,000 hits. And if you're crazy enough to dig deep into the result sets of Google and Yahoo!, you'll find that both pad their indexes with spam. For a search index, quality counts, and sometimes less is more.
It will be interesting to see how the search wars play out in the coming months. As the playing field becomes level with respect to speed and size, it seems clear that brand, relevance, and user experience design will be the keys to competitive advantage. What do you think?