tedster - 8:45 am on May 28, 2010 (gmt 0)
There could very well be something to that. There may have been a certain set of SEO "methods" that Google felt concentrated the long-tail traffic on too few sites (they do have a lot of statisticians on staff!) and they found a way to lessen that effect and spread the traffic around.
It's as good a theory as any I've heard - only trouble is, I don't know how to test it ;(
One key bit of knowledge could be what kind of pages lost their long-tail traffic. Has anyone who got hit seen any patterns they can report on? This thread should be a kind of think-tank, I'd say. we sure don't need the absolute definitive word - that's too much to hope for anyway.