Google USPA 20050071741

Interesting info on Google's site ranking:

Full article

Highlights:

• Sites can be ranked seasonally. A ski site may rank higher in the winter than in the summer. Google can monitor and rank pages by recording CTR changes by season.


• Changes in keyword density is monitored and recorded as are changes to anchor text.


• Clicks away from your site back to the search results are also monitored.


• User behavior in general could be monitored.

Much of this is in the interest of decreasing spam sites that warp Google's search results. It is, in essence, Google's defensive system, and requires Google to closely monitor the links that hold the internet together as well as the traffic through those links.