There is a nice thread over at SEO Chat Forums named Unique Content vs Reprinting Articles. In the thread, members discuss if it is better to write your own content or reprint (with permission) content already published.
As many of you know, I am all about unique content. I rarely republish anyone else's content, unless it is written specifically for this site. Why? Nothing at all to do with on-page search engine optimization. It is about you guys. I want you to have new, fresh, unique and (I hope) valuable content on a daily basis.
There is no doubt in my mind, since we have all seen it, that reprinted content can rank well and make money for the publisher. I like how Egol put it in message number 11;
You can reoptimize someone elses content, empower it with links and outrank the original. Still, you will always be in competition with all of those other versions of that content which are out there.
But normally, the "source document" (original content) gets a link back from the reprinted versions of its clones. If you are not actively in the mode of working to get links back to your articles and you do not "optimize" the content better then the source, it is more likely that the source will rank higher then the reprinted materials. Of course, there are tons of factors involved.
Think of it from a search engines perspective. Do they always want the original source? Or do you think they want the version that has the most value (i.e. user reviews, feedback, comments, links and so on)?