I scanned subjects files 2007.1-2007.47 too.  (As before, I'll be 
happy to look in earlier years if anyone is interested.)  Found 270 
records with "Google" in the 670, of which exactly one appears to be 
for Google books.  It's even less helpful than those cited from name 
authority records, because it doesn't mention the particular title anywhere:

         670:  : |a Google book search, Oct. 24, 2007 |b (<information>)

The remaining usages of "Google" in 670s in subject records are of 
the unhelpful "Google home page" variety:

         670:  : |a Google search, Oct. 3, 2007 |b (<information, 
without specific page identification>)

At 01:57 PM 11/30/2007, Adam L. Schiff wrote:
>I've cited some scanned Google books in subject authority 
>proposals.  The way I cited them was:
>670  <Title proper of book>, <year book was published>, via Google 
>book search, viewed <date of viewing>: $b information found in book

Gary L. Strawn, Authorities Librarian, etc.
Northwestern University Library, 1970 Campus Drive, Evanston IL 60208-2300
e-mail: [log in to unmask]   voice: 847/491-2788   fax: 847/491-8306
Forsan et haec olim meminisse iuvabit.          BatchCat version: 2006.51.826