Investors get behind podcasting, but will the listeners?

It was a milestone of some sort last month, when venture capitalists made the first two serious investments in podcasting start-ups. But did the milestone signify that podcasting is on the verge of dethroning radio -- or that the buzziest technology trend of 2005 had just jumped the shark?

In early August, PodShow raised $8.85 million from a group of West Coast investors that included Kleiner Perkins, Sequoia Capital, and Ram Shriram, an early supporter of Google and a member of the search site's board.

A few days later, Odeo cofounder Evan Williams announced on his blog that his company had raised money from Charles River Ventures of Waltham. Before starting Odeo in December, Williams had helped build Blogger, an early blog-creation and hosting site Google eventually acquired.

Odeo didn't say how much it had raised, but the Charles River partner who made the investment, George Zachary, told me it is ''in the same order of magnitude as the PodShow amount."

The entrepreneurs at PodShow and Odeo harbor big dreams for podcasting.

''Our mission is to bring as many people into podcasting as possible," says PodShow chief executive Ron Bloom. ''We think it has to be 100 million for the medium to take hold" -- that is, to sell advertising and sponsorships. (By comparison, commercial radio stations reach about 200 million listeners.)

Bloom started his company in January with his partner, former MTV video jockey Adam Curry. Curry, who now hosts a nightly program called ''PodShow" on Sirius Satellite Radio, wrote some of the early software that made podcasting possible.

Both Odeo and PodShow are headquartered in San Francisco. Both companies aim to make it easy for would-be talk show hosts to record, edit, and distribute their own podcasts, and for listeners to discover and download podcasts that appeal to them.

And both companies are excited about Wednesday's expected announcement of Motorola's ROKR cellphone, which was developed in partnership with Apple. It will be capable of playing podcasts and other MP3s.

''The syncing part is annoying to me," says Zachary, referring to the process of transferring podcasts from a PC to an MP3 player.

''The obvious place to keep podcasts is on a phone. Consumption and creation would be easier if done by phone."

The money and guidance that Odeo and PodShow will receive from their venture capital backers seem destined to turn them into the leading lights of podcasting, along with Apple's iTunes Music Store, which in June began distributing podcasts for free. (Another company to watch is publicly held Audible Inc., of New Jersey.)

''The money helps us go forward and explore possibilities, without having to choose one," says Noah Glass, the cofounder of Odeo and one of the pioneers of ''audio blogging," an earlier technology that never quite took off like podcasting. ''It gives us a little more agility and access to talent."

PodShow has already used its funding to acquire Podcast Alley, a popular directory of podcasts, and relocate its founder, Chris McIntyre, to San Francisco.

But podcasting is a phenomenon that has been attracting media attention faster than users. (Yes, I know I'm not helping the balance here.) A report from Cambridge-based Forrester Research projects that by 2010, about 12.3 million US households will be listening to podcasts; by comparison, Forrester expects about 20 million households to be listening to satellite radio by that point. That's far from Bloom's goal.

Apple made it easier to subscribe to podcasts by building the software into its iTunes Music Store, rather than requiring users to download a separate podcast-organizing application.

But there are other barriers to wider adoption. A listener's early experiences with podcasts need to be enjoyable, to keep him coming back for more.

''The first podcasts people encounter have to be much better," Bloom says. There's also a question of how listeners will react once more advertisements and sponsor messages start cropping up inside shows.

Then there's the hype factor.

''I'm concerned about the over-hype, and the bad quality user experience," says John Furrier, the founder of PodTech.net, a Silicon Valley-based site that features tech-oriented podcasts. ''I want to see more pragmatic utility. There's still a lot more work to do to make it mainstream."

I don't think that podcasting has jumped the shark. (I should perhaps disclose that while I've created a handful of podcasts for Boston.com and my own site, I don't have any kind of economic interest in podcasting's success or failure.) But neither do I expect it to replace old-school radio.

Podcasts will find a larger audience when they can be beamed automatically to a phone or wirelessly connected MP3 player, rather than downloaded from a PC. (I've largely stopped listening because of the hassle of syncing.) The Apple-Motorola ROKR phone is a good first step in that direction.

And it would help if more cars were delivered to showrooms with a built-in plug for MP3 players, as BMW, Pontiac, Honda, and Saturn have begun doing with some models. (People consume more audio while sitting behind the wheel than anywhere else.)

Still, not everyone will want to produce their own podcasts, and much of what is created will be entirely uninteresting to anyone who isn't related to the podcaster, and perhaps to some who are.

What's special about podcasting, though, is how it makes it simple for individuals or companies to express themselves and, if what they have to say is interesting, enlightening, or clever, to earn attention. You can point someone to a worthy podcast through a link on your blog, or an e-mail to a friend, in a way you could never point them to a snippet of radio. That's powerful.

Podcasting isn't about to kill radio or take it over, but as blogs are doing to publishing, it will make the radio industry reevaluate its relationship with the audience and leverage its strength as a mass medium.

One final coincidence:

PodShow has just moved its headquarters from Miami Beach to San Francisco, and it landed in offices in the South of Market neighborhood, which is also home to Odeo. A few weeks back, an Odeo employee was having lunch in a neighborhood restaurant when he spotted Adam Curry, and wondered whether something was up.

I mentioned to Glass that PodShow's new offices, in fact, were about a block away from his own.

''That's just too close for comfort," he said. ''I hope there are no bugs in the walls."

Scott Kirsner is a contributing editor at Fast Company. He can be reached at kirsner@pobox.com.