Bill Slawski - SEO By The Sea - should be voted the global expert on search engine patents. He keeps on top of them and is always breaking solid insights into how the patent applies to the various engines and ways to learn from them.
"A trio of patent applications from Google look at estimating the likelihood that an advertisement is a good one, in a method that goes beyond counting click-through-rates (CTR)."
They provide an extremely detailed list of factors that might go into a quality score, as well as details of different statistical models that might be generated from gathering information about those different factors.
A system provides one or more advertisements to users in response to search queries and logs user behavior associated with user selection of the one or more advertisements. The system also logs features associated with selected ones of the one or more advertisements, or associated with the search queries.
The system further uses a statistical model and the logged user behavior to estimate quality scores associated with the selected advertisements and aggregates the estimated quality scores. The system predicts the quality of another advertisement using the aggregated quality scores.