Andy Hagans has a nice post on Threadwatch about Quality Indicators in on-page optimization. I agree with him in that as this data is useful, its likely that it either does or may have some sort of impact.
IMO a search engine should use anything (legal) that it can to determine quality. Obviously link popularity and reputation is a big thing here, but so too are things like privacy policies, etc. to at least a small degree.
There are also some nice comments in the thread… especially via Randfish and a few others.