For companies trying to get viewers to see their posts, press releases, and advertisements, there are several factors and difficulties that must be taken into consideration. One of the most prevalent is the issue of duplicate content. Duplicate content is, just as it sounds, multiple postings of identical content in different places across the web. Where this becomes a problem is when someone searches for a portion of that content.
Due to there being so many copies of the same phrase or sentence, the search engine being used is forced to make a decision on which documents or pages to offer up as a result. Multiple pages that contain the same content are not all going to be listed as results, and so if the page you want to be seen is not the chosen result, it’s an opportunity missed. 
Situations in which duplicate content becomes an issue include:
- When a specific keyword is used multiple times in multiple cases, known as keyword stuffing. The repeated occurrence of that keyword may cause the search engine to disregard the page as less relevant duplicate content.
- Discussion forums which might have multiple URL’s that are very similar, though referencing different specific pages.
- Commercial items from a store catalog or online listings that have been uploaded in multiple locations under multiple URL’s.
- Multiple users linking to different pages of the same content, causing the content to show up on multiple pages in various locations. Even though the cause is completely innocent, it still manages to create a duplicate content issue.
- Misunderstanding of URL’s. Website developers may post content that can be accessed by two URL’s, considering that to be only one page. A search engine, however, will recognize duplicate content, as it searches by keywords and distinguishes by the URL’s.
- Printer content. Many sites will have printer-friendly articles, which have separate URL’s from the normal site content but contain exactly the same information. The two pages, often differing only by peripheral advertisement on the non printer-friendly page, may be recognized as duplicate content by search engines.
Google, being the leading search engine of the moment, is working hard to come up with ways of fixing the issues caused by duplicate content, and will presumably continue to do so as long as those problems exist. They address duplicate content on their website, dedicating an entire page to the issues caused by the problem.