What's A Content Spinner And Why Use One?
Although not widely known, content spinners have actually been around for a few years now. Article, or content spinning is using an original article as the basis to generate an unlimited number of new unique versions of the text. There are several content spinners available, and many considered them an essential tool for article marketing.

The new articles present the same concepts and ideas as the original, but written in different ways. They all are grammatically correct and perfectly readable, but each is unique, differing from the others in terms of the sentences and words used.

Why would you want to do that?

Simple: To avoid the duplicate content penalty at search engines like Google.
Let's say you've written an article. You've done your article directory submissions and the article has also been picked up by a few webmasters and used on their sites. When Google comes along and analyzes those pages, it can tell that they all contain the same content.

You might have heard that you don't have to worry about duplicate content because each page has other content on it in addition to the article.
Unfortunately, that's not the case.

You see, when it analyzes pages, Google doesn't simply compare the full text of the pages against each other, but many short excerpts from them. It then works out how many text snippets from the different pages are the same. A duplicate content flag is raised when the percentage of matches goes above a predetermined threshold.

In anycase, site navigation and other standard elements often account for much of the page content besides the article itself. Where it's the same on each page of a site, Google is usually able to differentiate it from the actual content and so discount in its comparison.

In the past you could simply replace words in your article with synonyms to avoid the duplicate content filter. That doesn't work anymore. Not unless it's done to the point that your article no longer makes sense to a human reader. And even then Google still might spot it. Gathering dust on my hard disk is a Windows application I bought which does that.

Having ascertained the pages it's looking at contain duplicate content, Google chooses the one it thinks is most relevant to the keyword phrase the searcher entered. It then filters out the other pages, usually leaving only the preferred article page visible in the results.

This means that if you have syndicated an article on your site, whenever the page of one of the other websites using it is considered more relevant to the keyword being searched than yours, your page simply won't appear in the results. It's your article, but someone else is getting the benefit ... not with you, but at your expense.

What Google Say About Duplicate Content
The duplicate content penalty isn't just a theory or something I'm making up. Google state that:
"During our crawling and when serving search results, we try hard to index and show pages with distinct information. This filtering means, for instance, that if your site has articles in "regular" and "printer" versions and neither set is blocked in robots.txt or via a noindex meta tag, we'll choose one version to list."

In short, where there are duplicates, Google picks one of them to display in the search results.
"In the rare cases in which we perceive that duplicate content may be shown with intent to manipulate our rankings and deceive our users, we'll also make appropriate adjustments in the indexing and ranking of the sites involved."
In addition, Google might take things further and make an adjustment to the rankings of entire sites it considers to be cheating. But just what is considered an "intent to manipulate our rankings and deceive" by Google?

Well, if your reasons for submitting to article directories include getting more backlinks in order to rank higher, you can safely assume you know at least one activity that is. A lot of the value of submitting is lost if those backlinks are discounted.
"However, we prefer to focus on filtering rather than ranking adjustments ... so in the vast majority of cases, the worst thing that'll befall webmasters is to see the "less desired" version of a page shown in our index."
Google tactfully omit to mention here that the "less desired" page may be on another site!