Okay I would not have bothered to read Yahoo's latest patent on reciprocal links if it were not for two blog posts by Bill Slawski and David Harry. These guys thankfully can interpret patent details in a way that does not make my head spin and explode.
I mean look at the abstract of Timothy Converse et al application:
"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. "
David gets the nod for the most entertaining read - he even includes a cartoon - while detailing how the excess reciprocal links are spotted and flagged. Explaining three way link schemes and "suspicious clusters".
Bill, on the other hand, gets the tip of the hat for his detail in simplifying various link related patents; taking the jargon and explaining it in terms even I can understand.
He notes - as does David - that:
"If the links between pages (or domains or hosts) is a small percentage of the links on each page or domain or host, the process described in this patent filing may not kick off. I say “kick off” because this is an automated process rather than a manual review at this point.
If the percentage of links is larger than than, a number of steps might be taken by the search engine.
The sites might be reviewed manually by “human investigators” or they might be examined by a program from the search engine that has been trained to look for signals of suspicious activity."
Both articles should be read, despite the fact that they address much similar ground. With their different ways of explaining by the time you are done you will have a firm grasp of the state of reciprocal links as seen by the major search engines, Yahoo in particular.