It sounds really neat, and is certainly attracting some press attention. I haven't had a chance to properly get into it yet, but will.

The New York Times and Scientific American have both written about it (these articles each have a Page 2 as well, clickable at the bottom)

http://www.nytimes.com/2010/12/17/books/17words.html?scp=1&sq=500%20billion%20wo

http://www.scientificamerican.com/article.cfm?id=google-books-culture

And there's another piece in Discover Magazine (please excuse non-clickie but the URL is so long I'm afraid it'll constipate the Link Maker):

http://blogs.discovermagazine.com/notrocketscience/2010/12/16/the-cultural-genome-google-books-reveals-traces-of-fame-censorship-and-changing-languages/