Online marketing research firm eMarketer released its latest report Wednesday, a study that indicates a growing number of Americans Internet users are publishing their own blogs, for a growing blog-reading audience.

The cloyingly named The Blogosphere: A-Twitter with Activity, report indicates that the number of American Internet users making their own blogs is growing: 27.9 million US Internet users have a blog (updated at least once per month), accounting for 14% of the Internet population. By 2013, the study predicts a blogging population of 37.6 million (or a projected 17% of the Internet population).

More interesting to bloggers, podcasters, and other media creators, is the study’s analysis of the growing number of blog readers.

eMarketer estimates that in 2009, 96.6 million US Internet users will be reading blogs (using their threshhold of “at least once per month”). By 2013, the study predicts that 128.2 million people, or 58% of all US users, will be reading blogs.

“Blog sites now touch tens of millions of people in the US, and the numbers of blog readers and creators are projected to continue growing,” says the study’s author, Paul Verna.

“Blogs are now mainstream media,” said Richard Jalichandra, CEO of Technorati. “You’re also seeing mainstream media coming in the other direction by adding blog content.”

This point of view is echoed by David Tokheim, of blogging platform Six Apart Media. “The lines are becoming blurred between a standalone blog that might be created on TypePad or Blogger or WordPress and blog content that’s created by The New York Times.”

Study author Verna says, “today’s [blogs] are about two-way conversations that take place on many fronts: independent, standalone blogs; social networks; e-commerce and mainstream media sites; and microblogging platforms such as Twitter….This blogging activity presents new opportunities for marketers to influence—and monitor—conversations that may be relevant to their businesses.”

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