We all know Google's take on duplicate content, it is not spammy, it is not something they have penalties for unless you are being completely evil. We also know that if you have exactly the same content as someone else, it might be hard for your content to rank in Google because Google shows only one of the duplicative pages.
The new news is that Matt Cutts of Google said that somewhere between 25% to 30% of the web is duplicative. Meaning over one-quarter of the pages, content, files, images, etc, on the web are replicated. Can you imagine?
It might seem like a lot to a normal user. Probably doesn't seem like a lot to you and me because as soon as I publish this story, 15 other sites will scrape it and post it on their sites. So this one piece of content will be duplicated 15X or so.
But as a user, because search engines cluster and show one of the duplicative pages, we don't realize that so much of the web is duplicative.
Cool, no? Depends if your site is the one that makes it to the top.