Do Search Engines Penalize Duplicate Content ?

What do search engines do when they detect duplicate content at multiple places ?

Brian Brown says - "Rather than penalizing sites or Web pages, the search engines filter out those pages that they consider to be duplications, placing them further back within the search results. If the pages you want to show up first don’t or other sites rank higher for the same content, then the engines may be seeing it as duplicate content and filtering appropriately.

If you still think your site is actually being penalized because of this, you can try searching in the search engines for the page title, a section of content, or the URL of the page. If your page has been indexed, but doesn’t seem to appear for these searches, then you may be looking at more than just a filter. However, at this point, it would be good to review other issues that might have garnered a penalty, such as other negative practices, like hidden links." Link.