"It seems like every company has a blog section of its own, and is also interested in what the blogosphere is saying about it," said Paul Verna, senior analyst at eMarketer.

Word-of-mouth is still a powerful marketing tactic, and since influential bloggers are so effective at spreading the word about their likes and dislikes, blogger demographics continue to matter. So, excluding major businesses and splogs, who blogs now?

Although most researchers have noted a young skew to the blog audience, a BIGresearch study found that the average age of adult bloggers is actually 37.6. (see chart on left)

A Deloitte & Touche study of blog usage by age found a direct relationship: the younger the user, the more likely he or she was to read or keep a blog on a weekly basis. For example, 55% of millennials (ages 13 to 24) surveyed read a blog, and the percentages declined for every age cohort in the study until reaching just 16% for matures (ages 61 to 75).

Similarly, 35% of millennials kept a blog, whereas only 1% of matures did. The age groups in between—Generation X (ages 25 to 41) and baby boomers (ages 42 to 60)—fell between those two extremes.

With regard to the ethnicity of US adult bloggers, BIGresearch found that 69.7% were white, 20% were Hispanic, 12.2% were African-American and 3.7% were Asian. These percentages were essentially in line with the US Census Bureau's most recent estimates of the demographic breakdown of the US population, allowing for differences in methodologies, mixed-race respondents and overlap between Hispanics and individuals of other ethnicities.

Once a haven for techies, there are now blogs for everything from celebrity gossip to political commentary to the most mundane personal minutiae. By 2012, more than 145 million people—or 67% of the US Internet population—will be reading blogs at least once per month.

The number of people creating blogs in the US will also grow, reaching 34.7 million people by 2012—16% of the Internet population. By contrast, there were some 22.6 million US bloggers in 2007, a number that correlates to 12% of Internet users.

Buoyed by these massive levels of consumer engagement, US blog advertising will reach $746 million in 2012, up from $283 million in 2007.