...in other words, even if it's been pulled down 1,000 times, there's a good chance nobody wanted your specific book.
I really believe there's nothing, ultimately, to be done about the masses distributing copies of, well, everything. On the other hand, freely distributed doesn't mean not paid for: plenty of folks who saw Dr. Horrible's Sing-a-long blog did so where there was advertising, or bought the DVD (I did). The last Harry Potter book was available online before release, and did that really affect sales in any way?
Some folks won't pay. Wouldn't have. Some would have, but they won't if they can avoid it. In any case, there's no way to stop them. Stopping the search engines assumes that a solution could be found that wouldn't be worked around: don't be silly. This is the way it is.