In six years, blogs have gone from navel-gazing online diaries to must-read Internet publications that rival the reach and influence of traditional media properties.

A new study from online research firm comScore Networks Inc. reveals that 50 million U.S. Internet users visited blog sites in the first quarter of this year, up 45% from the first quarter of 2004. That represents about 30% of all U.S. Internet users, or a sixth of the total U.S. population.

The study is based on data from comScore's opt-in research panel. The panel tracks the online activity of 1.5 million U.S. Internet users and reflects the behavior of consumers who visited the 400 top Weblog properties and blog-hosting services during the first three months of 2005.

Given their popularity, the study suggests that blogs can now be thought of as part of the mainstream media.

Top Ten Blog Hosts

1. blogspot.com

2. livejournal.com

3. typepad.com

4. xanga.com

5. AOL Journals

6. blogs.com

7. MSN Spaces

8. blogdrive.com

9. greatestjournal.com

10. diaryland.com

DATA: comScore Networks

There are approximately 14.7 million blogs, if one goes by blog search engine Technorati.com. But it's the top blog properties that are growing the fastest. The study finds that six of the top 10 blog-hosting services have seen their traffic numbers grow by more than 100% from the first quarter of 2004 to the first quarter of 2005. For example, according to comScore, Blogspot.com now draws more traffic than NYTimes.com, USAToday.com, or WashingtonPost.com.

New York University journalism professor and author Adam L. Penenberg sees the increasing popularity of blogs as a sign of disaffection with traditional media coverage. "I think the public's appetite for consumer-created content on the Web (like blogs) mirrors its taste for reality shows, celebrity gossip magazines, talk radio, and cable TV shows," he says via E-mail. "The public craves intimacy. We want to feel like we know the people we read and read about, listen to on the radio, watch on TV, and click to on the Net."

"Mainstream media outlets should realize that objective 'just the facts, ma'am' type of journalism isn't compelling enough anymore--and is, in fact, a major turn off to younger audiences, which are their future subscribers," he says.

Rick Bruner, co-author of the report and director of research at Internet advertising company DoubleClick Inc. (which wasn't involved with the study), sees blogs complementing traditional media rather than competing with it. "I think it's much more of a symbiotic relationship than one transforming the other," he says.

The public's embrace of blogs is particularly significant for marketers, Bruner says. As the study notes, bloggers represent an attractive audience in demographic terms. They tend to live in wealthier households, be younger, favor high-speed Internet connections, and be more likely to shop online.

Such statistics haven't been lost on forward-looking advertisers. Late last year, Nike launched a blog (now inactive) called "Art of Speed" with the assistance of Gawker Media to promote a series of short films about speed (and, obliquely, about its shoes). Lee Dungarees has a blog called "90 Ft. Babe" that features posts by "Natalia ... an unusually tall model/actress" whose avowed interests include "cute guys, shoes, my favorite lip gloss, chocolate!"