Sometimes it feels like the internet's just the same thing over and over. Google agrees: According to the search giant, 25-30 percent of everything online actually is a duplicate of something else somewhere else online.
On the GoogleWebmasterHelp YouTube channel that you didn't know existed, engineer Matt Cutts turns to the mailbag to answer a frequently asked question regarding how duplicate content affects a site's SEO. It turns out that Google doesn't see dupes—like blockquotes, reblogs, reposted images, etc—as spammy content. Instead, the mysterious Google algorithm groups all of the duplicated content into a single lump and attempts to surface the best of it.
How Google deals with duplicated content isn't all that surprising, it's just crazy how much of the information out there is just a copy of something else. [Search Engine Roundtable]