There are really two parts to this question. We need to think about duplicate content on your site and off your site.
When we think about content on your site, a common mistake is having duplicate title tags and meta descriptions and having these site wide. It’s definitely a good idea to make sure that every page has its own unique titles and descriptions. This is very quick and easy to fix and will almost immediately improve your rankings.
Now, I don’t believe Google “penalizes” those who are doing something wrong nearly as much as people might think. Instead, Google works more like a “filter”. If you have duplicated content, Google may filter out those pages, but they’re not going to get removed from the index or anything.
Often e-commerce sites get it wrong because their descriptions are duplicated throughout the site. They may even copy their vendor’s products and descriptions directly.
This leads into part 2 of this question. Is it going to be an issue if other people have the same content? Again, I’m quite sure that you’re not going to get a duplicate content penalty from Google.
Repeated content is part and parcel of the way the internet works. For example, when you’re doing a press release, it’s distributed to hundreds and thousands of outlets and it’s all the same press release.
We’ve run some tests where we’ve distributed a release through PRWeb.com and we’ve seen hundreds and thousands of creations of that one article all linking back to our website with the same content! Surely you couldn’t argue that this is going to hurt our rankings.
In short, I do believe that this whole idea of duplicate content is overplayed. And like most things in SEO, with enough link building, even if it is the same content, you can still get those pages to rank extremely well.