Robert_Charlton - 6:59 pm on Aug 29, 2012 (gmt 0)
Google have been trading traffic for data
Shaddows - One of the more intriguing of your many helpful observations.
I find it is more likely that people in North America to be logged into Google while searching
Mobile is another group that would not return referrers. Might mobile searchers be a piece of the puzzle here, either as a subset of the North America searchers, or as a separate group in the UK?
Assuming that mobile might be implicitly geo-skewed, I'm grasping also at geo factors being a strong element in traffic shaping and trying to connect the dots. How might geo relate to other aspects of what's happening in this case, including the drop-off of long tail?