Here Google defines a factor called UA [update amount], & it can be a factor that they weight differently for differ segments of the page.

PAGE SEGMENTATION and RATES OF CHANGE

Here is my paraphrase for some of the paragraphs I found interesting:

trust and authority of linking sites, spikes in back link growth, spikes of similar anchor text, and so on.

The patent mentions some of the standard factors we already talk about

With the current update apparently doing "something different" with backlink, I went back for another reading of the 2007 patent application

Google's Patent on Backlinks - many interesting clues from 2007

Each company will maintain its own separate display advertising business and sales force.

Yahoo! will become the exclusive worldwide relationship sales force for both companies’ premium search advertisers.

Yahoo! will continue to use its technology and data in other areas of its business such as enhancing display advertising technology.