Studies have shown that conservative bloggers cite other conservative blogs and include links to them in their blog rolls; liberal bloggers likewise segregate their references and citations. This point Cass Sunstein makes in Infotopia: How Many Minds Produce Knowledge (Oxford 2006) at 190.
A test of this proposition would be the set of blogs I have identified as written by current or former in-house counsel on law department operations (See my post of Jan. 28, 2009: law department management blawgs with 11 references; May 16, 2011: blawgs by in-house lawyers past or present with 16 references.).
If someone assembled all the blog rolls of the site and counted them, it would probably show a core of blogs that frequently cite and link to each other as well as a long tail of infrequent sites.