To give some comparison and contrast to the shrinking cable news ratings noted below, here's some new figures regarding blog readership, authorship, and commenting from the Pew Internet and American Life Project. From a ComputerWorld account:
Blog readership jumped 58 percent between February and November and included 32 million U.S. citizens in 2004. More than 8 million U.S. citizens have created a Web-based diary, and one in 10, or around 14 million U.S. Internet users, has contributed thoughts or comments to a blog.
[Link via Rational Review.]