The Pew Internet and American Life Project wants to know:

By the end of 2004 blogs had established themselves as a key part of online culture.

Two surveys by the Pew Internet & American Life Project in November established new contours for the blogosphere and its popularity:

• 7% of the 120 million U.S. adults who use the internet say they have created a blog or web-based diary. That represents more than 8 million people.
  
• 27% of internet users say they read blogs, a 58% jump from the 17% who told us they were blog readers in February. This means that by the end of 2004 32 million Americans were blog readers. Much of the attention to blogs focused on those that covered the recent political campaign and the media. And at least some of the overall growth in blog readership is attributable to political blogs. Some 9% of internet users said they read political blogs “frequently” or “sometimes” during the campaign.

On the other hand, the study also finds that a majority of internet users -- 62% in all -- have never heard of a blog.

You should check out the whole piece. It's extremely informative and tells us a lot about the type of people (like us) who are getting their news on blogs.