It appears many sites with duplicate content and bad business practices were penalized with no recovery even a year later.
The reason … Google’s algorithmic changed. This isn’t the first, but it was one of the hardest hitting when it comes to how many pages of your site Google is indexing.
Here is a great article showing you the time consuming steps to slowly regain some of your exposure:
Things we can do to fix:
1. Better Content
2. No Farm links
3. No Short Posts (300+ words)
4. Don’t overly optimize called Black Hat SEO
5. Duplicate content will affect your search engine presence – use URL canonicalization
6. Social Media Helps! Google+ votes, Facebook likes, Twitter and Delicious
Just a few bad pages affects the entire site – it is a domain level penalty.