Websites that have earned trusted status are often treated differently from those that have not.
SEO’s have commented on the double standards that exist for judging big brand, high-importance sites compared to newer, independent sites. For the search engines, trust most likely has to do with the links your domain has earned. If you publish low-quality, duplicate content on your personal blog, then buy several links from spammy directories, you’re likely to encounter considerable ranking problems. However, if you post that same content on Wikipedia, even with the same spammy links pointing to the URL, it would likely still rank tremendously well. Such is the power of domain trust and authority.
Trust can also be established through inbound links. A little duplicate content and a few suspicious links are far more likely to be overlooked if your site has earned hundreds of links from high-quality, editorial sources like CNN.com or Cornell.edu.