Banking on a similar effect, in February, the parent company of the web magazine Slate — which has been producing podcasts for years — created Panoply, a network of shows it produces with media partners, including The New York Times. Matt Turck, the chief revenue officer for Panoply, said the audience for Slate’s own podcasts grew from two million downloads a month to six million downloads a month in 2014. By combining many shows into a single network, Panoply hopes to sell a single large audience to advertisers.

Neither Panoply nor Gimlet would discuss revenue or profits in detail, but both said the advertising business was booming. Podcast advertising has been dominated by a regular cast of mainly tech companies looking to attract a relatively wealthy audience with an affinity for technology. Firms like Audible, Stamps.com, MailChimp, Squarespace and several apparel and food companies are regular sponsors. More recently, podcasts have also begun to attract large entertainment marketers — movies and TV shows now advertise on podcasts — and even large national brands like Ford and Acura have sponsored shows.

Several advertisers told me that podcast ads had proved to be tremendously effective. They can’t be easily skipped, and because they are often read by hosts, audiences are often convinced of their authenticity. “We feel it creates a deep personal connection to our brand,” said Ryan Stansky, the marketing manager who runs podcast advertising at Squarespace, which currently sponsors hundreds of podcasts.

Even though rates are high, selling ads is still a laborious process and top-tier shows limit the number of ads that appear in each show. The more ads that appear, the less each advertiser will pay, a dynamic that may limit the upside of the business. There are also technical problems to be solved. Podcasters can count their downloads, but it’s difficult to tell if downloads translate to listeners, and it’s nearly impossible to tell who is listening, and to figure out what sort of ads listeners may like. There are also few standards in the business, which means podcasters and advertisers are often suspicious of one another’s claims.

“I’ve heard directly from sales reps in casual settings that numbers get lied about,” Mr. Stansky said. “I’ve heard that from the other side — sales reps that I’ve worked with saying, ‘Yeah, we lied to you about numbers.’ And to me, that’s the most scary part of it all, that you’re paying for something that you’re not actually getting.”

Podcasters concede that dodgy numbers are a problem, but they argue it is one that will be solved as the business matures and technology improves. Several advertisers, including Squarespace, create “offer codes” or specific web links to promote as part of their ads — a way to track how many customers podcasts bring to their sites. Larger advertisers like Ford said their investments in podcast marketing are small, so the numbers aren’t being watched closely. And the Interactive Advertising Bureau, an online ad trade group, is creating standards for podcast audience measurement.

In other words, there is a lot about this business that still needs to be worked out. This will most likely happen eventually. Podcasting is destined to be huge, both as a medium and a business. “It’s the future of radio,” Mr. Turck of Panoply said. Just don’t expect that future to come tomorrow.