AlyssaS - 10:43 pm on Feb 12, 2011 (gmt 0)
This bit is interesting too:
On Feb. 1, the average Penney position for 59 search terms was 1.3.
On Feb. 8, when the algorithm was changing, it was 4.
By Feb. 10, it was 52.
The Feb 10 bit is the manual penalty. The algo change only moved them down a little bit, which indicates that G is being cautious.
Perhaps what's happened is something like this: they detect some spammy words on a page, are not sure whether that means there is an absentee blog owner/lack of moderation, or if the links are paid, and decide to only assign half the weight they normally do to that page, so the "juice" that is passed on is diminished.
If all your links are from pages like that, you suffer badly, but if you have some other decent links, you still rank, just not as well as before.