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size is only one dimension of the quality of a search engineI would guess that Google's index is bit larger than 8 billion but that it doesn't really matter much.
They only tend to update it when another search engine declares they have the biggest index.
With all the extra pages they'll have from Google Sitemaps, I expect they're ahead of Yahoo!'s figure.
By comparison, Google said it tracks 11.3 billion objects. That figure consists of the nearly 8.2 billion Web pages that Google proudly touts on its home page and 2.1 billion images, with the remainder of material coming from its group discussions.
I'm not attacking genuine Adsense publishers with genuine content making an extra buck, but the reality is that Adsense has spawned a disastrous problem that G can't fix - or at least are in no rush to fix.