I feel like for the longest time we grew accustomed to a falsified index. When Google started adsense it paved the way for spam in the form of mfa and content farms which I'm sure compiles a majority of the index. Ever since adsense the index has been jaded.
Now all of the sudden they decided, "hey we do search let's focus on search again" as stated by MC recently, and decide to devalue all of the spam we've been seeing for years in one giant swipe. I think for Google it's a big strike in taking their index back however seeing as these pages and the links within them made a majority of the index we're seeing a monumental shift in results. These devalued pages affect every site for whom's content they scraped.
In my case I have really great content which as a not-so-sincere form of flattery has been scraped by thousands of websites. I had achieved pretty good rankings until this update thanks to the thousands of links that spam created.
The other day I lost 35% of my traffic all at once. Can't wait to see the full impact is once the change is international. I'm all for Google dealing with the scrapers and content farms, but I feel they fell asleep at the wheel. This change could have been done in bits and pieces or something that wasn't so drastic.
The path I chose and have always chosen for 10 years is Brett's old post about ranking in Google in 30 days or whatever it was. Great post I guess as long as your content didn't get scraped along the way...