I’ve found a couple of interesting early citations on information diffusion. This from “Person to Person Communication of News,” by Bradley S. Greenberg, from Journalism Quarterly, 1960:
“It appears unwarranted, or at least insufficient to index a news event’s importance in terms of the number of persons who are aware of the event. This grants equivalence to the assassination of a President and the extra-marital ventures of film celebrities.”
He goes on to suggest two distinct classes of news that spread well through personal channels: big news, or breaking stories (e.g. the Kennedy assassination) which spread very rapidly, and reach high levels of saturation, and those that are perceived to have functional importance to a specific subset of the population (e.g. a teacher noticing stories topical to schools). The third defunct category of news are all other stories which are not spread at all through peer-to-peer communication. The boring stuff.
Weblogs, being tools of peer-to-peer communication seem to support this categorization, pulling both topical and “big” news items. I tend to favor an alternative classification based on context: for every interest a person has, there is an associated context. “Big” news stories are of the type that appeal to the most general context, that of being human, being from a particular country, or having a specific ethos. The “bigness” of a news story is simply related to the number of people that share a given context.