martinibuster - 8:44 am on Sep 1, 2011 (gmt 0)

as they were mixed with other types of link building

That's diversity. Linking patterns can be mapped. It's like the Touch Graph [touchgraph.com]. A site that has reciprocated backlinks will resemble a closed unit, like a cultivated garden bordered by a stone wall. Is that what the backlink profile of a typical site resembles?