Microdoc News: Dynamics of a Blogosphere Story is an interesting analysis of how memes spread via blogs.
A couple of key points:
Rarely can an individual blogger get a story going. It is far more usual that several bloggers blog about an occurrence, an event or a comment elsewhere and then after that bloggers in groups get going.
The best blog stories are those that are branded with a word or phrase that is highly identifiable with that story. The blog stories that die the quickest and sometimes are not even summarized are those that are either very technical by nature, highly polemic (almost quackery), or are so bland as not to be worth writing about.
The stories that get going are not usually subject specific blogs but stories that cut across all interests of the blogging community. A medical, technical, or other type blog does not make it big, for example. But stories about blogging, human rights, world events, or the human spirit that apply to everyone, tend to become big stories.