Earlier this year, the Pew Internet & American Life Research Project released a study showing that teens aged 12 to 17 and young adults aged 18 to 29 (the latter often classified as Millenials) are the biggest Internet-using demographics. Of those two groups, the younger one favors social networking over just about anything else, including blogging.

Remembering also the Kaiser Foundation survey, which claimed that many teens spend upwards of seven hours a day consuming digital media, we’ve got a strong picture of the human race’s fully connected and massively social digital future.

Whereas those two surveys portrayed young people mostly as media consumers and social networkers (the Pew report found that kids don’t blog or tweet as much as their immediate elders), a new study released on eMarketer suggests that Millenials, at least, are huge readers and creators of blog content.

Researched by BlogHer and iVillage and co-sponsored by Ketchum and The Nielsen Company, the study found that 40.4% of the 18-to-29-year-olds surveyed write blogs — that’s two fifths of all blog writers in the study.

The most popular blog subjects were “Express myself” and “For fun.” The least popular: “Earn money” and “Persuade others,” though a fifth or more do blog for those purposes.

But what about the kids?

As ReadWriteWeb points out, the survey left out teens under 18 — the so-called “iGeneration,” that’s so hooked right now on social networking sites, especially Facebook.

The Pew survey showed that a majority — 62% to 80% — of 12-to-17-year-olds engage in social networking. And you know who gets this? Facebook.

The world’s largest social network has been blowing up headlines the past week with its overtures about making the Internet more social through things like its “Like button for the Internet.”

They may or may not create as much of their own content (both macro- and micro-blogging), but kids definitely share content and interact with each other in increasing numbers the social web.

And if there’s one thing we’re learning, the future of online consumption is definitely becoming more social.

Put that in your pipe … and share it.