Jenna Wortham describes her start in podcasting, just a couple of years ago.

“I used to do a late-night show called Heartline with a friend out of a shipping container in Bushwick. We would sit and play music and our friends would come. We had the highest, most trafficked show on the Bel-Air Radio Network,” a community radio station.

“People would call. We would give out advice and talk a lot about technology and the Internet. My friend, Steven Avalos, who now works at Netflix, and I had a great rapport and that was really nice.”

Last week, the 32-year-old New York Times Magazine staff writer begins to cohost Still Processing, a just-launched Times podcast. Well promoted, it should find a sizable, national audience almost overnight.

Hers is not an uncommon tale out of these still early days of podcasting. Podcasting inspires the kind of Judy Garland let’s-put-on-a-show spirit we saw in 1939’s Babes in Arms. Anyone who’s anyone is doing one, it seems.

Podcasts ooze with life at this moment in the culture. Informal, casual, often funny, sometimes revealing, they offer us a seemingly direct human touch, through voice, as we buzz through our days. It’s people talking to people, seemingly without anyone in between.

That’s an illusion, of course, as it is with all media. It’s the mediation — the organization of communication — that makes our connections possible. They may not get top billing, but the middlemen, the business builders, compel our attention.

In this series, we’ve taken a snapshot of a podcast industry in the process of a birth. Three years ago, anyone calling it an industry would have been scoffed at. But even as ad money grows — it may top a still-small $200 million next year — entrepreneurs have flocked in. And therein lies our tale.

Even the business people professionalizing this cottage industry voice concern about how it will evolve. They don’t want to see podcast’s spirit devolve into something like its primary predecessor.

“Everyone is so sensitive that [commercial] radio is a terrible listening experience,” says Sean Carr, CEO of emerging podcast platform company Art19.

The phrase of the moment, both from some in the trade and from many of the millions of listeners who’ve become podcast addicts, seems to be: Don’t screw it up.

So what indeed might podcasting look like in the next several years? Clearly, it’s only the echelon of the top few thousand podcasts that will win big audiences and generate significant ad dollars. How many of the other 90-percent-plus of podcasters — hundreds of thousands of them — will maintain their voices and their regular shows?

One estimate, from Libsyn’s Rob Walch: The median number of downloads for any podcast episode is 173. The top 20 percent get 1,400; the top 10 percent get 3,900.

It’s those top podcasts, though, that are defining the new business. The very company names that aim to brand, corral and birth new ones speak of the unlimited potential now seen. Wondery. Panoply. Gimlet.

On a whiteboard, their optimism sketches out. That math — only 57 million Americans listen to even one podcast a week — seems to offer a boundless horizon.

That’s another illusion, of course, but it’s a happy one. It’s way too early to forecast the boundariess of this podcast revolution. It was only 23 months ago that Serial spellbound a nation, and helped birth this new industry, with 8 million people downloading each eagerly awaited first-season episode. Though there are many Serial wannabes, we already see more than a few breakout hits. As everyone eyes growth ahead, they’ll have to see how podcasting hours fit into our busy lives, especially as the second golden age of high-quality TV generates more couch-based binging. Let’s also recall that Internet usage shows some sign of peaking; we’re still stuck with only 24 hours in a day, and Arianna Huffington wants us to sleep through more of them.

In talking with more than three dozen podcast executives, their conviviality stands out. It’s a rising-tide-lifts-all-boats mindset, one markedly different from the zero-sum approach that now consumes many digital media executives. Podcasters don’t feel Facebook and Google looming over their shoulders, though they might want to keep an eye out for them in the rearview.

It’s a wide-open world, freed from the constraints of terrestrial radio. PRX veteran Jake Shapiro sums up that new freedom best. For years, he encouraged outside-the-box audio production, but he had to try to convince institutionally conservative station managers the shows were worth airtime.

It was killing us. We were sitting on a goldmine, and we were trying to push it through a straw. This was convincing local program directors to format and try out innovative audio. You had to be an optimist to do what you were doing, but it was kind of the dark ages of saying, “Yeah, we have all this stuff. It’s not on public radio, but it is…It’s a public medium, and we have this catalog.”

Now, though, thanks to that great liberator/destroyer of old systems. the Internet, it’s a new world. “This is not like the independent film world, a YouTube ecosystem,” says Shapiro. “It’s way smaller, but it has some of those ingredients now in a way that you can see starting to gel and thrive.”

In this new formation, getting big is much on the minds of many. The new Podtrac rankings certify the effort to be among the biggest, which is driving the formation and expansion of new networks. The mainstreaming of dynamic ad insertion multiplies the places ads can go.

If that hockey-stick growth in both ad revenue and audience defines this moment, it’s also spawned an arms race. The shift from analog to digital, and the efficiency it demands, both forces and enables companies to build, before the business of the spoken word inevitably slows. We’ll see which of the models — purer content houses like a Gimlet or This American Life/Serial, network plays like Panoply, Pandora One, or Wondery, or the various public radio players — emerge ahead.

Then, in the background, are the guys who are really big. Any of Spotify, SiriusXM, or Pandora could follow Audible’s move into podcasting in a more serious way, bringing their great scale of audience and advertising to bear.

And there’s the perennial question of Apple, sitting fat and dumb in the midst of podcast plenty. Some emerging podcast networks advocate Apple taking on more of a tech-and-payment middle role, akin to its iTunes and App Store businesses. Will Apple consider that business big enough to be worthwhile? And what kind of impact might that have? Learning the lessons of digital media generally, podcast executives know they should try to avoid having their products disintermediated by digital giants — but they, like all, are still entranced by their platforms and power.

Podcasting’s growth as an island of media has served its programming well and led it into unforeseen directions. As the business builds bridges to the rest of digital media, how will the island evolve?

Panoply’s Jacob Weisberg rightfully brings up one fundamental question of the role of scale in this particular medium. I asked him if he thinks listeners will gravitate to a show because it’s a Panoply show.

I think so, but it’s not clear how that’s going to shake out. In the world of books, nobody cares if something is published by Viking or Random House. They care about the author and the book. I think podcasting is going to be more like that. Panoply wants to have a certain reputation for doing high quality shows and maybe for doing certain kinds of shows. [PRX’s] Radiotopia obviously does that, so I think you’ll have these pools of styles of podcasts, but ultimately I think it’s the shows that are the brand, not the publishers.

That interplay between brand and show poses both huge opportunities and challenges for two of the public radio behemoths, NPR and WNYC, who have taken early leads in podcasting. The two cooked up much of the early stew of culture/interviews/news/identity that defined much of early podcasting. Both now produce dozens of shows, and keep launching more.

For public media, podcasting has offered an unexpected chance at reinvigoration, of a way to get younger in audience.

“It’s a way to bring people into the public radio system. It’s also a way for us to bring new talents and new voices into public radio,” says Loren Mayor, NPR’s COO. “We are seeing in our data that the audiences for podcast are significantly younger than the audiences for radio. We’re also seeing that podcast listeners are just more likely than the general population to be younger listeners overall.”

As we’ve noted WNYC’s crossover point — seeing more of its sponsorship and underwriting now come from digital, driven by podcasting, than from broadcasting — we see a public media model in transition.

NPR’s Jarl Mohn and WNYC’s Laura Walker find the tempo of old business/new business decision-making accelerating. A key question there is which parts of the business to emphasize. Programming? Delivery and distribution? Talent building? Can they do all of those successfully? Can they retain their strong positions in podcasting as new entrants come at them from every corner?

Those decisions include their relationships with local public media stations. The old model of licensing NPR- or WNYC-produced shows for local airing will clearly have to be rethought, as more consumers go direct to the shows of their choice whenever they want.

Then, there’s the eternal question of digital media: local. It’s where we live, and where our ears are most of the time. But as a digital business, podcasting rewards scale, and that’s why almost all new production is aimed nationally, and at niches within national. Across the country, though, we see regional podcast innovation.

In Boston, WBUR has built a substantial podcast presence, first taking its winning top local programs national, like Car Talk and Only a Game. Now it can point to the success of its Modern Love collaboration with The New York Times and its own Dear Sugar, a “rampantly empathic” advice show that has won big audiences.

Iris Adler, program director at WBUR, talks about podcasting as a means for the public media leader to “get out of the wheel.” That wheel is the schedule of public radio program scheduling, national and local, that has long constrained and defined public radio. Now, she says, WBUR can get “younger, more national, and more diverse” via podcasts. This fall, it plans two new shows.

At Austin’s KUT, Texas Standard — a standout daily news program — has used its daily podcast to extend its audience by about 17 percent. Monthly, it reaches 350,000 listeners by broadcast. Almost 60,000 monthly take in a podcast, and soon that audience will be sold to sponsors as well. In Oregon, OPB debuted a new food and wine podcast this week. And in L.A., KPCC’s The Frame provides a smart take on the film industry, a local show with some national reach.

One big question here: How can podcasts help reinvigorate local media, at a time when print newspaper companies just shrink away? That’s just one of the public service questions here: the mission question.

Podcasting may seem like a mission-driven business to many, but, in fact, it’s far wider. Comedy has driven much of the early business, and now true-crime-plus networks like Wondery look more like basic cable than This American Life.

While there may some among us who relish both the profane nostalgia of Gilbert Gottfried’s Amazing Colossal Podcast and NPR’s searingly reported Embedded, the meeting of higher and lower brows here will be quite watchable. As new apps make the discovery of new shows easier, will the movements of new podcast listeners change the programming of the trade?

For those of us focused on journalism — and especially original reporting — the jury’s out. Reveal’s ambitious effort at a weekly 60 Minutes-like investigative show has gained some traction, and has a few fellow travelers. Shows like Embedded — led by All Things Considered host Kelly McEvers — point out a way to do reporting differently, and could be a model used to figure out a new paradigm for local reporting as well. But how much money — funded by whom — will be available to help develop that model?

Then, there’s the harder-to-define role of podcasting in explaining the world to us. NPR’s Planet Money still lights a path here, building on the now eight-year-old Giant Pool of Money episode that broke new radio ground in both explanation and reporting on the Great Recession. That This American Life-produced show opened many eyes to how radio, reporting, and down-to-earth presentation could be harnessed in the new world — a feat that TAL still manages to pull off week after week.

At its best, podcasting chews on the dizzying level of change in our culture, our politics, our tech, and ourselves. In this moment of so much change and consternation, that may be its greatest social contribution. It’s a mirror of us, at this moment, and that’s worth remembering as we chart its business fortunes.

The research for this series was commissioned by Public Media Futures Forums, a project funded by the Wyncote Foundation to support in-depth analyses of strategic challenges facing public media. The analysis was done independently and without any foundation review.