All of the fascinating things about signals are confidential for all of the reasons listed in the article, and Google has been sued so many times by sites that think they should rank better than they do that I can't really give examples.
I think it's safe to say though that there are a lot of people worried about and thinking hard about what the web is turning into and how to rank it appropriately.
Most of the content is no longer written by devoted hobbyists, people no longer link as often to things they like, and much of the content on the front pages of reddit, digg (and sometimes even hackernews) was put there by people trying to make your search results worse.