Found this post very interesting regarding the decline of trust in search results. Source was USC research. Findings:
The survey found that only 51% of people trust information provided by search engines, down from 62% in 2006. Google, as the most popular search engine in the United States, isn’t trusted by nearly half (49%) of the people who use it, an interesting result.
... this despite ...
The Internet is perceived by users to be a more important source of information for them — this over all other principal media, including television, radio, newspapers, and books.
I would expect a fairly strong indirect correlation between search result trust and the extent of SEM/SEO and rank gaming. Maybe Jason is right.