fifi - 1:17 am on Jan 9, 2011 (gmt 0)

Thanks for the link. Our situation seems different than the issue presented in the throttling thread, since we have had our sites for a range of time between three years and younger, and have never seen anything but steady growth in traffic from google, up to the point where we did about 8 million visits network-wide in november. of that, 80-90% is from google. Starting in Dec, all sorts of chaos broke out. Google de-listed some of our sites entirely, but left other, nearly identical, sites running.
Then, many of the sites exhibited the wild swings that I describe above. My theory is that google is playing with its algorithm, but doing limited rollouts. The theory is that sites we have that are in one cluster of google's world get to be guinea pigs for the algorithm changes, with wild and unpredictable results.
I was wondering if other webmasters had seen any radical changes in their level of search traffic starting in late nov or early dec. Some of the yo-yo ing described above seems to sort of match our pattern.