Comment on Duplicate Content Penalty SEO by Bruce Bates.
Duplicate content is not within and of itself a penalty. Duplicate content exists across a wide range of sites and can be a good thing for the originating site. Its a great thing when google see’s 500 of the same article published on the internet, because it ranks the date those articles were published and gives precedence to the original website.
This is why duplicate content seems like a penalty. When you use content that has already been used in other places, you no longer get the benefits from it. Its like a vote for the original site. This is why its absolutely wonderful to publish articles on article directory sites, but not so wonderful to use the articles found on article directory sites.
There is so much confusion surrounding what duplicate content is, that I think more people need to get into the details because its not as obvious as one may think.
