walkman - 6:45 pm on Jul 15, 2011 (gmt 0)
November 2011: New stats for Google's search index
4,501,701,451,854,019 pages and around
4,501,701,451,854,019 subdomains, give or take a few.
To be treated like, say, Wordpress, they probably have to keep the subdomains separated, not heavily interlinked and articles in the same major category.