Search Engine Penalty for Duplicate Content

Search engines never duplicate content. However, having your content duplicated elsewhere online will diminish your credibility in the eyes of search engines for many reasons.
Search engines consider duplicate content as a spamming activity intended to trick the search engines into ranking you higher.

Search engines want to be with websites that has good quality and original content.
Sometimes it is alright to publish articles with similar content to your WebPages but not all the time. Popular article submission banks such as Ezine Articles and Buzzle often get spotted for similar contents by search engines and others.

If the content is good, articles banks will use this information from Ezine and Buzzle and include it in their database of articles. This is acceptable as search engines view this as a testament to your credibility and the quality of your website content.