Several publishers are speaking up to say that Google Book Search has actually helped increase book sales.
Despite fears from the publishing community that Google's book scanning projects will hurt sales and lead to exploitation of their content, small publishers Oxford University Press, Springer Science and Business, German publisher Walter de Gruyter/Mouton-De Gruyter, and historical warfare publisher Osprey, say they've seen a steady increase in referrals from Google Book Search.
According to Reuters, specialty publisher Springer Science + Business reported sales growth of its backlist catalog using Google Book Search, with 99 percent of the 30,000 titles it has in the program getting viewed, including many published before 1992.
The Reuters article doesn't directly address whether larger publishers are seeing an increase in sales. Looks like it's mostly specialty houses that are seeing the uptick, which is to be expected. I'll bet that most large publishers declined to give numbers or have already opted out of Google Book Search. As reported earlier, publisher HarperCollins is building their own online book search tool.
Meanwhile, Google is still being sued by the Author's Guild and the Association of American Publishers for infringing on copyrights with Google Book Search.