I run a blog directory where each blog has its own details page. This page contains traffic stats, blog description, and a place for users to leave reviews. It also grabs their 5 most recent posts from their feed and displays a short excerpt. Do you think that displaying their most recent posts with excerpt might be seen as duplicate content and penalized?
The answer is yes, google panda is kicking those content farm. That's why you can see article directory are losing their good serp on google search engine