bluntforce - 7:18 am on Nov 22, 2012 (gmt 0)
I don't see it as controversial, I think there's no clear definition between throttling and zombies. I see them as two distinct issues.
I look at Bing/Yahoo user referrals in relation to Google referrals. If Google was time or user limit throttling, there should be a point in a day where Google referrals drop in relation to Bing/Yahoo. I haven't seen that, I see fluctuations, but Bing/Yahoo referrals remain consistent on a percentage basis with Google referrals.
Perceived throttling as a byproduct of reduced exposure(links) is something I'm looking at.
I sometimes wonder how many zombies are HTTP/1.0 vs HTTP/1.1