Transparency of source is a good thing.
That said, the algorithms of Google aren't "content cops" that are designed to protect searchers from "shilled" vs. "professional, traditional and legitimate" editorial content. The algorithms of Google are engineered to help searchers find the most relevant and helpful content related to the query they are typing into the search box. And many times, the most valuable content comes from "the source."
And another thing: Wasn't the "nofollow" attribute developed to combat specific types of link spam, especially comment spamming? When the problem is such a black and white, good vs. evil thing as combating comment spam, it's easy to agree on what should be done.
I believe the topic of whether there is value to the consumer (or reader, or search engine user) in content created by sources other than journalists is a more nuanced issue.
This is a fair point. Your average Stanford or MIT press release about a scientific paper, say, is more information-rich than the summary that most newspapers or blogs would provide of it. Nonetheless, do such press releases or advertorials belong in "Google News," a product that is nominally exactly for "professional, traditional and legitimate" sources?
Relevance, too, in the two-audience (machine and human) world is tricky. Google is using keyword density and other sophisticated methods, but can do little to detect what, to a human reader, might be an obvious bias or conflict of interest. That kind of consideration should play into Google's "relevance" algorithm, but so far as I know, it doesn't.