Foreign Policy magazine has an article about blogging written by two well-known scholar-bloggers, Daniel Drezner and Henry Farrell, that provides a valuable reality check:

Even the most popular blog garners only a fraction of the Web traffic that major media outlets attract. According to the 2003 Pew Research Center for the People and the Press Internet Survey, only 4 percent of online Americans refer to blogs for information and opinions. … [A]n October 2003 survey of the blogosphere conducted by Perseus concluded that “the typical blog is written by a teenage girl who uses it twice a month to update her friends and classmates on happenings in her life.” Blogging is almost exclusively a part-time, voluntary activity. The median income generated by a weblog is zero dollars.

Why, then, are blogs are becoming internationally influential? Easy:

Increasingly, journalists and pundits take their cues about “what matters” in the world from weblogs. For salient topics in global affairs, the blogosphere functions as a rare combination of distributed expertise, real-time collective response to breaking news, and public-opinion barometer. What’s more, a hierarchical structure has taken shape within the primordial chaos of cyberspace. A few elite blogs have emerged as aggregators of information and analysis, enabling media commentators to extract meaningful analysis and rely on blogs to help them interpret and predict political developments.

[ADDED 8.1.2006]