Whoa - 7:56 pm on Feb 27, 2011 (gmt 0)
Econman, I'm not sure we'll ever know all the quality factors that come into play, but, off the top of my head, I'd be asking questions like these to assess quality:
What percentage of your site's pages have content that is identical to content on other sites for which that same content predates your content?
What percentage of your site's pages have content that is very similar to content on other sites for which that same content predates your content?
What is the average ratio of original content to non-original content for pages on your site?
What percentage of your site's pages appear to be dynamically created from a database with similar phrasing, or slight variations thereof, on every page?
What is the ad space real estate to content real estate ratio on your pages? Is it too high?
Is your site overoptimized, suggesting that you may be more about SEO than good content?
Do you have reader comments on your pages, suggesting that they find some value in your content? What's the sentiment of that content?
What percentage of pages on your site have some proof points of engaged and interested users who appreciate your content?
Are your related links to other internal pages hand-crafted and relevant or do they appear to be computer-generated to randomly spread link love to other parts of the site?
Do you have footer links that might suggest you are selling links? Are there footer links on other sites that might suggest you are buying links?
Does your site have quality signs that suggest that it is maintained well and updated often with fresh relevant content or is it static?
Is there evidence of stub content – questions asked with no answers given?
Are visitors returning to your site?
How long are visitors staying on your site?
Do they leave your site and do the same search again?
Probably lots of others...