A couple of threads from past few days speculating on how G may be basing evaluations on sites rather than pages from sites. The first, from WMW has Tedster musing ''brainstorm: How might Google measure the site, and not just a page?' ...
This is my conjecture, but what if Google is now working with domain-wide semantic factors a bit more strongly than in the past?
Some are seeing a strange trend toward SERPs that rank higher level pages that are actually one click away from the real "meat" - now what's that all about?
A DigitalPoint member writes that he originally had managed an AdWords campaign across several domains and received a "Great" quality score for his keyword groups. However, ever since he has begun consolidating his AdWords campaigns on one domain, his quality score plummets.
Clearly there is a domain name Quality Score that is affecting us. It seems when using individual domains names the success or failure of an individual ad group/keyword does not affect the others, but when it all goes to the same domain name it seems tied into each other.