tedster - 9:16 pm on Jun 6, 2012 (gmt 0)
Geo-targeting basically generates different search results based on the IP address of the user. Of course, it also depends on accurate tagging of the geographical relevance of each website, too.
I think any apparent traffic shaping may be based more on other kinds of taxonomy, not just geographic. Google does build automated taxonomies that they use to tag websites, users, and query types. I honestly can't see them intentionally mis-matching those tags. However, I can see accidental mis-matches occurring. And I can see that there could be statistical testing of these taxonomies, just to verify or question an original automated determination - a sort of machine learning.
Even though that model of mine could explain short term zombie traffic, I can't see why it would go on for months or years - and just for some sites.