A new Gallup poll (reported by Jim Horton) reinforces data collected earlier this year by the Pew Internet and American Life Project. Most adult Americans don’t read blogs, and a lot of those don’t even know what they are.

Three-quarters of the U.S. public uses the Internet at work, school, or home, but only one in four Americans are either very familiar or somewhat familiar with blogs (the shortened form of the original “Web logs”). More than half, 56%, have no knowledge of them. Even among Internet users, only 32% are very or somewhat familiar with blogs.

In reporting these findings, Jim Horton notes, “Lest we get too messianic about blogs, we should remind ourselves they are still the buzz of the chattering classes and of the young,” and points to this Gallup finding:

Blog readers are younger than the population at large. Although 17% of the public is aged 18 to 29, a quarter of all blog readers (those who read even occasionally) are in this age bracket. At the older extreme, 17% of Americans are 65 and older, but only 6% of blog readers are this old.

Hmm. Well, I’m over 50, so I fit somewhere into this 6% number. But ultimately, the impact of blogs—and why PR people need to pay attention to them—has little to do with how many people actually read them. When an issue raised in blogs makes waves that capture the attention of mainstream media, the consequences are felt well beyond the blogosphere. Just ask Dan Rather, who also doesn’t fit into the 18-to-29 age bracket.

It’s not at all uncommon for the original source of influence to be invisible by the time that influence reaches its peak and the fallout begins. A lot of people know that CNN’s Eason Jordan lost his job; it’s simply not relevant that most of those people remain blissfully unaware that blogs played a key role, or even know what blogs are. As long as bloggers wield influence over outcomes, it simply doesn’t matter that most people don’t read them. We need to factor them into our thinking and planning regardless.

Even Gallup writes, “The apparent effect that blogging is having within media and political circles is far ahead of its direct impact on the American public.”

I also have to wonder how many of those three-in-four adults who don’t know what a blog is read one anyway. I’m reminded of the focus groups I witnessed in Virginia last year during which most teenage participants weren’t able to tell the faciliator what a blog is, but once it was described, they knew exactly what she was talking about: “Oh, you mean my Live Journal” or “Oh, you mean a Xanga.” How many adults read blogs without knowing that’s what they are? After all, they look for all the world like Web pages.

Of course, readership in all age brackets will increase. We saw this on the World Wide Web which, in its early days, was surfed mainly by the young but now has become a common appliance for all age groups. The young, as a group, are more amenable to trying something to new; we older folks (sigh) tend to be more set in our ways. But once a channel has become a default part of the landscape, we all begin to use it.

So blogs are just as important in light of this study as we thought they were before. Don’t be lulled by numbers until you’ve thought through what they mean.