Black Hat SEO: Duplicate Copy/Content

If you know anything about writing copy for websites, you know you can't pull (or scrape) content from other sites and put it onto your own. That's considered duplicate copy by Google, and warrants a serious penalty from the search engines that could sweep that page off their index indefinitely. Not to worry—Google tries its best to determine where the copy originated so that Webmaster is not unfairly penalized.

For most site owners/developers, this is old news. What a lot of Webmasters are still worried about is duplicate copy as it pertains to groups of URLs. When the same page can be accessed via multiple URLs, Google tends to group those URLs into a cluster to avoid redundant search results. If you don't tell the search engines what the best URL for that group is by including it in your Sitemap, they'll pick it themselves.

Check out Google's own article on this topic, which is eye opening but also unleashes a Pandora's Box of Webmaster interrogation:

Demystifying Duplicate Content