tedster - 12:34 am on Oct 4, 2011 (gmt 0)
First, some pages and keywords get hit harder than others.
Tedster - Any theories on why Google is hitting so selectively?
Here's my take on it. Panda is neither one - not just a site focused algorithm and not just a page focused algorithm either. It looks at BOTH!
A set of low quality pages can poison the rest of the site - there's a kind of decaying negative factor that spreads through the sites internal linking. Google doesn't want to send visitors to poor quality pages (no matter their relevance score) and they also don't want to send people to pages that are neighbors to those poor pages, either.
At the same time, it is possible for a page here or there to stand out as being really top quality, and they can get lifted over and above the general demotion that most of the site suffers.