In the current issue of Advertising Age, you'll find a piece titled "YouTube Stars You May Not Know -- But Should." I was tipped off to the existence of this story by … me (I wrote it up based on suggestions from colleagues).

Having watched countless hours of YouTube videos while trying to help decide the handful of rising stars we'd end up highlighting, I think I've gained some insight into what, exactly, is going on with this whole "YouTube stars" phenomenon. Namely:

These are truly mainstream stars
In each of the write-ups for our chosen YouTube stars, there's a line that starts, "Mainstream media that should sign them." For instance, globetrotting British wonder twins Jack and Finn Harries of the JacksGap YouTube channel would be a perfect fit for Travel Channel.

But I have to confess that in a way it's kind of confusing to talk about mainstream media as the "other" in the context of these YouTubers, because they're already mainstream stars -- and YouTube itself is obviously mainstream media that's completely permeated global media culture.

Just look at the scale and reach of the content these folks are producing. The number of people who have subscribed to their channels range from 2.9 million to 14 million; the view counts on their video libraries range from 156 million to 1.6 billion.

These are pros
How do you get to be huge on YouTube? Beyond the requirements usually associated with media popularity -- be appealing, have some modicum of talent, have something to say, find your niche, etc. -- you've gotta work. The YouTubers in our package derive their incomes primarily through the YouTube Partner Program, which serves up targeted ads on their videos and gives them a cut of the revenue, and there's no faking it when you're your own boss. They often have very rigorous, self-imposed posting schedules that they've stuck to for years; they're clearly aware that they're suppliers of programming and that their fans are counting on them.

When I mentioned to a colleague that Ad Age would be calling marketers' attention to rising YouTube stars, she compared YouTubers to wild horses that brands and agencies would try to tame and "break." I get that -- these personalities are beloved for being themselves, for being unfiltered, so the presumption is that it can be risky to attempt to work with them; i.e., that marketers will end up getting kicked in the head.

But I look at these YouTube stars and I see plenty of discipline, resolve and careful modulation of message. Even Jenna Marbles, the comedic YouTuber with 1.6 billion video views to date for her wry, foul-mouthed commentaries on pop culture and girl culture ("How To Throw a 4th of July BBQ With Iggy Azalea," "What a Girl's Eyebrows Mean"), is clearly playing a character that fits neatly into a time-honored entertainment-industry continuum that extends from Joan Rivers to Sarah Silverman.

Besides, plenty of marketers have gotten kicked in the head by supposedly polished, media-trained stars who've come up through the traditional celebrity-industrial complex and then spectacularly crashed and burned.

YouTube stardom has a lot to do with selfie culture
One surprising thing to me as I watched a lot of videos from YouTube stars is how long they are. Supposedly everyone is so ADD-addled these days that all we want, at least online, is "snackable content," and yet our group of YouTube stars routinely post videos that run nine, 10, 11 minutes or more.

Finn Harries of JacksGap recently told The Guardian, "Google allows us to see how long people watch for. The average engagement of those people is 13 minutes, out of a 15-minute episode."

Keep in mind that, while the Harries twins have graduated to doing beautifully shot and edited travel videos and other adventurous content, they started out basically sitting in their bedrooms, often not doing much more than talking to the camera.

And that's still the m.o. of the rest of our YouTubers. They sit and perform for the camera.

Some of these videos almost come off like FaceTime or Skype sessions with particularly charismatic friends. And that's how I think their fans -- the completists who watch every video and watch them to the end -- receive these chunks of content. They're consumed as intensely personal one-on-one dispatches that, paradoxically, often have more reach than many shows on national cable networks.

These are selfies in video form, basically. Once you accept that premise, then it's easy to understand how these voluble, rambling and, yes, self-absorbed YouTubers fit perfectly into the media zeitgeist circa 2014.

Simon Dumenco is the "Media Guy" columnist for Advertising Age. You can follow him on Twitter @simondumenco.