diberry - 2:59 pm on Jul 23, 2012 (gmt 0)
Panthro, there are two phenomena people have noticed:
--Traffic Throttling: where Google just seems to stop sending searchers on a dime at some point in each hour/day/week.
--Zombie traffic: the searchers keep coming, but suddenly none of them convert. It's like you're getting a whole different, bad quality of traffic.
Your theory might explain the first IF everyone feeling it has had a penalty. I feel I'm being throttled, and I got the "no manual penalty" letter, but others can chime in. (After all, I may be wrong about my throttling - my searches are so low, it's hard to get reliable statistics from them.)
But I don't think your theory would apply to the second, and that's the one we're mainly talking about in this thread (although there's some overlap, so both versions do come up).