Podcasts have been compared to television in the 1940s, and for good reason: The medium is entering uncharted territory but has the potential to rival terrestrial radio.

During the past two years, while the radio industry has obsessed over formats and a flawed ratings system that often fails to accurately gauge audience numbers or demographics, podcasts of the comedic variety have flourished. Adam Carolla and Marc Maron lead the pack, following the pioneering path cleared by Kevin Smith, Ricky Gervais and Jimmy Pardo.

The numbers tell the story: Carolla, who bid farewell to 15 markets when his syndicated CBS Radio morning show was canceled in 2009, has amassed an audience 10 times as big with his daily podcast. The Adam Carolla Show has logged more than 50 million downloads in a year; Maron's twice-weekly WTF is at 20 million and counting. Both are offered for free, while archived episodes (like Maron's intense 2010 interview with Robin Williams) cost $1.99 at iTunes (no money changes hands between the programs and Apple, but server space is the responsibility of show producers and can get pricey at about $10,000 a month). Cash starts flowing when listenership hits certain benchmarks and advertisers come calling, which, according to Carolla, they have -- big time.

"A lot of it is performance-based, and our audience performs," says Carolla, the former Man Show and Loveline host who spent about $125,000 of his own money in the podcast's nascent days and whose advertisers include ProFlowers.com and Nissan. "It's more accurate than radio, where there's so much BS about cumes, time spent listening, people filling out Arbitron diaries with golf pencils. ... With podcasts, you can tell how many shows have been listened to, down to the click. That's better for the sponsors and for us."

The beauty of the podcast is its simplicity: Anyone can purchase a microphone and mixer, and the cost is nominal compared to a traditional radio program. "With an investment of $700 to $1,000, you can make a show," says Maron, whose podcast regularly charts in the iTunes Top 10 and charges $1,000 to $15,000 per sponsor. The comedian conducts interviews from the garage of his Los Angeles home, but he's rarely there these days as demand for his stand-up shows (which often double as podcast-recording opportunities) has jumped by 50 percent. "I'm now performing in rooms," cracks Maron. "When I started WTF, I was a marginal character who couldn't get booked -- a respected but acquired taste, not a seller of tickets. Now, I can sell pretty good."

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"As a singular business, a podcast might not be profitable, but if you look at other revenue streams that can grow from it, it definitely is," says Judi Brown-Marmel, partner at Levity Entertainment Group, which manages such comedians as Jim Breuer and Hal Sparks. "Who it serves best are the people that don't fit a traditional broadcast model. Like, if George Carlin were 22 today, what would he be doing? Probably a podcast."

Beyond the spoken word, the ripple effect can bring revenue from merchandising, book deals (Carolla's New York Times best-seller In Fifty Years We'll All Be Chicks was released in 2010, and Maron is working on his first book for Spiegel & Grau), iPhone apps (after Apple and Google take 10 percent, revenue is split 50-50 with the developer) and sales of comedy albums. Maron, in an ironic twist after being told in 2009 to ride out his contract at the now defunct Air America, has returned to terrestrial radio through NPR, which pays to air edited versions of WTF. Currently, 13 public radio affiliates carry the PRX version.

Of course, not all podcasts are created equal. Greg Proops, who hosts cult favorite The Smartest Man in the World, says what he makes from his Proopscast "is not even gas money. I do it because a couple hundred thousand people will hear me, which is more than all my gigs combined." Maron says his initial goal was to "make an honest buck" and pay his mortgage. And now? "I'm making a living because I've been able to book more work, but it's still just me and a guy in my garage."

In contrast, Carolla also works from his garage -- "He's got a bunker!" mocks Maron -- but he employs 18 people, from "$10-an-hour guys" to those "making six figures." "It's a business," he says. "Madison Avenue and corporate America are already involved. I don't know how to define success, but I can tell you that 18 months ago, companies like Nissan or LegalZoom didn't exist in our podcast world. Now they're in it in a big way, and other companies are coming on board."