dickbaker - 12:02 am on Mar 3, 2011 (gmt 0)
I agree with what The Mad Scientist is pointing out, and I'm certain that my site is an example of one of the sites that has good quality pages mixed in with bad.
I've noticed something of a pattern to the amount of ranking drop, and I think it could have something to do with variations in page quality as some percentage of the overall site. In looking at pages that were on page one for certain phrases, some pages were dropped to #12 or so, some to #24 or thereabouts, some to #45 or so, and some to #70 or even worse.
The pages that went to #12 or so are pages that brought in a lot of traffic, amounts of traffic that were proportionately higher than other pages. The #12 rank almost seems like a "the page is good, but we had to hit it because of other pages on your site" demotion.
The pages that dropped much further have what could be problems, even though they were page one last week Wednesday. The ones that really dropped need a lot of examination.
The question now is whether to wait to see if Google does some re-ranking before making adjustments to the worst pages. I'm tempted to make changes to pages that never ranked too well just to see what would happen, with or without a re-ranking.