The Business Of Burying Internet Search Results
npr.org
npr.org
http://seoblackhat.com/2009/07/22/google-bowling-what-is-it-...
http://seoblackhat.com/2009/07/10/link-pyramids/
If you check the backlinks of many mainstream sites that compete for common keywords (anything pharmaceutical or related to gambling for example) you will see this sort of thing setup. However, as this is still a tricky practice, most sites will make sure that they are never getting more than about 1/5 of their incoming links from their pyramids.