From this thread:
http://www.webproworld.com/viewtopic.php?p=261217
It has often been speculated that Google has weighing factor in its algorithm called Trust Rank. Their has been evidence found before that Google employs many, many human editors to assign weight of "trust" to certain websites, for certain popular keywords. This is fact. Google does do this. How much this affects the algo, who knows. The opposite is probably true as well. As these editors "stumble" upon bas websites Crap Rank is probably assigned to them.
Another way to describe this is calling a website an "authority" on the query or subject searched. Personally I feel "authority" websites are those that have been given a "golden seal of approval" by Google. Websites like Amazon.com, Walmart.com, eBay.com more than likely have higher weight in the Google index for any number of keywords searched. The reason for this is obvious...these are established websites that would not look to "do wrong" to the Google SERP's in any way. Now of course these websites do have to compete with the rest of use, but I feel this "authority" rating given to them can give them the extra jumps/bumps they need to get ahead of your regular mom and pop websites.