The name of the paper is Blogs and the Economics of Reciprocal Attention. What it says is that the most successful bloggers will participate in their blogging network more than those that do not. Blogs that link to other blogs and bloggers that comment on other blogs are cited as ways to reciprocate. Hat tip to Freakonomics (even though they talk bad about real estate agents).
I have always taught the people just getting into the blogosphere that they must read and comment on other blogs 5 times as much as they write on their own.