Rros no sidewides, all single votes from themed pages. They take a dying domain and load it up with 50 category pages, on each one is a huge amount of content that appears to be scrapped from dozens of sites and then dynamically mixed together. A search will yield two sentences from about 5-6 different sites but the entire thing is broken language. On that page will be three to five links back along with 2-3 links to other parts of the link farm. Each page showed over 100 domains linking to each. Complex, well thought out scheme. There are no ads, no other information. Clean CSS and text, php hosts but stripped pages. Each day hundreds more appear.
Shaddows. A fair share of our traffic is now bing and yahoo. It's increasing month to month. On the days that we have poor google conversions we also have poor bing coversions. Dating back many years the same weeks seem to have this happen. I cannot make the same connection you can on out company site. However I do see one related effect.
We sponsored a scholarship for the first time for a major university. They wrote a very nice article which appeared recently and has stayed on their front page of the department site,in context and by company name only. Our educational traffic went through the roof with google. Probably not a coincidence.
What you report in detail has been noted by many. Maybe what we are seeing is sites fail the test.