Yahoo's patent for Reciprocal links

Yahoo! has filed a patent on reciprocal links: “A method for identifying reciprocal links is provided. At a particular host, the set of hosts which link to the particular host and the set of hosts to which the particular host links are determined. The intersection and union of the two sets of hosts are also determined, […]
Yahoo! has filed a patent on reciprocal links: “A method for identifying reciprocal links is provided. At a particular host, the set of hosts which link to the particular host and the set of hosts to which the particular host links are determined. The intersection and union of the two sets of hosts are also determined, and the sizes of the intersection and union are calculated. The concentration of reciprocal links at the particular host is calculated based on the sizes of the intersection and union. A ratio of the intersection size to the union size is used to determine the concentration of reciprocal links. The particular host's rank in a list of ranked search results may be changed as a result of identification of a high concentration of reciprocal links.”