Google has never much liked duplicate content, they've never made any secret of the fact that they penalise sites with large chunks of content that have been plagiarised.
The reason for this is simple, before duplicate content penalties came in to force a simple way that unscrupulous web marketers could get high search positions was to simply cut and paste the content from whichever site ranked top for the search terms they were chasing.
Penalties for cut and paste content are variable, but the rule of thumb is don't do it. This is even more important now that google's "farmer" update is coming. The update to google's algorithm went live in the USA last week with the express purpose of removing sites of low value and it's expected to hit the UK and Europe soon. Sites with large amounts of cut and paste content are sometimes referred to as "content farms", hence the name.
It's not yet clear exactly how google is defining "sites of low value" but heavier penalties for sites that plagiarise fit with what the US bloggers and analysts are reporting.
So what exactly is duplicate content and more importantly how does google decide? In a nutshell it's anything that has been copied from another website, there are no hard and fast rules but in general things like copying a sentence and quoting it in a larger article is ok. for example this quote from google's own webmaster tools site is ok:
"Duplicate content generally refers to substantive blocks of content within or across domains that either completely match other content or are appreciably similar."
However the larger the block that you copy and the less original content you have, the more likely you are to be penalised and find your site disappearing from the search results.
I often get asked by clients who are pushed for time if they can just "copy someone else's text and change a few words".
No, no you can't. Google's algorithms are smart, they will spot this a mile off.
Another common suggestion is "can I just copy someone else's content for now and change it later?" Again, not a good idea. Although restoring the position a site that has been penalised is possible it's not easy and there's no guarantee that it will work.
So the bottom line is this:
Write original, good quality content.
I know it's hard, I know it takes time, I know it can be expensive, but why risk your shiny new website being relegated to page 10 of the search results where no one will ever see it?
