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Panda is a ranking reduction that can effect an entire site.  It is believed to occur when a site has a lot of duplicate content. So, if you post a lot of duplicate content on your site you should not be surprised to see a ranking reduction occur.  You might avoid the problem if you post the content with noindex.... maybe. Also, if you  are linking straight to the duplicate on a more powerful site that almost guarantees that your version of the content will be at least filtered.