Manual Action Penalties can be Applied to Thin, Spun or Aggregated Content
Thin content penalties can be applied to sites manually by the web spam team where the entire site seems to be thin, ‘spun’, or aggregated from other sources without any unique additional value.
Google Considers Amount of Unique Content Per Page and Number of Pages with Unique Content
Google looks at how much text on each page is unique, and how many pages have unique content.
Return 404 or Noindex for Empty Pages
Google prefers you to return a 404 status or add a noindex for empty pages, like category pages with no items listed, even if temporary.
Soft 404 Errors Can Identify Thin Pages
The Soft 404 errors report in Webmaster Tools is a good way of identifying thin pages which Google don’t think have any original content.
Add Content to Thin Content Pages
A case study involving Matt Cutts found very thin content pages (e.g. regional branch pages) were not ranking. After adding more unqiue content, the pages performed better. So Google still requires a minimum amount of unique content per page.