On any site I have that no longer is receiving measurable quality traffic from Google, I’ve blocked Google.
Some of the sites have great original content that people like and use as shown by the direct hits into the site via bookmark or otherwise.
Google can be a knowledge engine all they want but not with my content.
In the beginning, it was a great relationship. I provided Google with good quality content to index and they provided me with good quality traffic to my site. Since that relationship no longer exists, I have no reason to provide content that Google may or may not use in their ever knowing “Knowledge Engine”.