From Site Reference.com

Well, on March 31, 2005, Google applied for a patent on its latest search algorithm. For those who have no fear of their brains exploding from buzzword overload do a search on “Patent Application 0050071741” to read the entire patent. The patent application describes 'a method for scoring a document comprising: identifying the document; obtaining one or more types of history (sic) data associated with the document; and generating a score for the document based on the one or more types of historical data.'

http://www.site-reference.com/General/11255/index.html

What all these "takes" fail to mention is that the patent is dated December 2003. So anything mentioned in it will have likely been implemented, improved, tweaked, updated and possibly taken out of Googles ranking algo by now.