Its the Farmer 3.0 Update. Silent but deadly. Most of the people here felt it because majority run sites that have thousands indexed and some multi-millions of pages indexed. The SEO world doesnt even know this update even happened.
Farmer update from Google is basically deranking and putting into check, sites that are basically content farms. Little to no information + faking headers to manipulate SERPS to get the 'spammy, no content' page indexed. Seriously you ever tried searching for shit before this update?
You'd have the first 10 sites all DDL/scraper sites like filestube, heroturk, etc... and if you goto that site, the damn page has NOTHING IN IT. If you goto these sites via SERPS you'd hit ANOTHER damn search page with basically all your search terms. For instance you search 'gotta get the money ebook' (example) and the first 4 results are filestube, 5th and 6th, 7, 8, 9th are some other DDL type sites. If you click on filestube, you hit a page that says Search found: gotta get the money ebook and list about 10 other SPAM sites that make you run around in a damn circle.
As google stated
http://www.google.com/support/webmasters/bin/answer.py?answer=66361
Google will take action against domains that try to rank more highly by just showing scraped or other auto-generated pages that don't add any value to users. Examples include:
Auto-generated content: Content generated programatically. Often this will consist of random paragraphs of text that make no sense to the reader but that may contain search keywords.
I believe soft 404 pages / generated pages from search constitutes this.
Now I'm sitting here thinking, ALL the other sites that manipulate searches got penalized. But FILESTUBE has not. They either got lucky or something else...
I know for certain, certain sites like heroturk and freshwap was manually hit. But filestube really bugs the shit out of me, as they are probably the worst site ever.