The Portable Media Expo kicks off Friday in Ontario, California, with all the earmarks of success. But the proceedings could see some last minute competition from one of the biggest names in the fast-growing podcasting business: former MTV VJ Adam Curry.

Some 2,500 attendees and 50 exhibitors from 38 states and 22 nations are expected to turn out for the event, which organizers are billing as the world's first podcasting convention.

Although Curry plans to attend the show, he has declined to speak at it or sponsor it. And now he is threatening to hold an impromptu "un-expo" at a nearby hotel, where podcasters may be invited to discuss potential promotional deals with his company, PodShow.com, Curry spokesman Aaron Burcell told Wired News on Tuesday.

"They've been trying to back us into a huge sponsorship by saying we're not supportive of the expo, that we're this and that," Burcell said. "But we have a lot of podcasters who are part of the Portable Media Expo and we've been very supportive. It's not wise to try to extort the company that's been most supportive of the podcasting community."

Burcell accused convention organizer Tim Bourquin of retaliating against Curry for refusing to sponsor the trade show or to speak at it. He also alleged that Bourquin had been bad-mouthing Curry and his company to podcasters who belong to a PodShow stable of talent known as the Pod Squad.

Bourquin flatly denied he's contacted any of PodShow's talent but acknowledged he questioned on the most recent episode of his Podcast Brothers show why PodShow hadn't sponsored the program and why Curry had declined to address the event. Bourquin said PodShow had demanded a free high-level sponsorship in exchange for some help with promotion and a speech by former MTV veejay and self-anointed "PodFather" Curry, but Bourquin said he rejected that offer because his event has become so popular he no longer felt he needed Curry as a headliner.

"They're upset that I'm not bowing down to them," Bourquin said. "Everyone who gets a call from Adam and PodShow is impressed and feels important. I don't fall all over these guys when they call me. I gave them several opportunities to be involved and they repeatedly turned me down."

Burcell said Curry is for now scheduled to attend the event, if not address it, and PodShow is organizing a pre-convention event on Thursday showcasing musicians who allow podcasters to use their recordings for no charge. He added that the company was interested in buying the title sponsorship for the show, but was beaten to the punch when Audible.com sewed up a deal months ago for $35,000.

For Bourquin, the hullabaloo amounts to an unneeded distraction in the waning days before a trade show that has grown beyond anyone's expectations. When he conjured up the notion of a trade show focusing on portable media a year ago, the word "podcast" was hardly even part of a techie's lexicon and the notion of a video iPod was a glint in Steve Jobs' eye.

Even six months ago, Bourquin looked ahead at his Portable Media Expo with a mixture of excitement and anxiety, hoping merely to meet his initial goal of 1,000 registrants. He's more than doubled that goal in a show that is drawing executives from Yahoo, Whirlpool and Disney as well as a list of new startup companies primed to make a litany of product announcements. A healthy roster of keynote speakers from NPR's Robert Spier to This Week in Tech podcaster Leo Laporte are also on tap.

"This has certainly grown beyond our expectations," said Bourquin, who, along with his brother Emile Bourquin, co-hosts the Podcast Brothers podcast, a show that offers advice on how to promote and monetize podcasts. "It just shows what's been happening in this business."

Tradeshow Week associate publisher Michael Hughes, whose trade publication tracks the conference business, declared the expo off to a "very good start" with more than 2,000 attendees. Hughes noted the average trade show size attracts 4,000 registrants.

"It's a challenge to launch a new trade show because most sectors are already covered," Hughes says. "You really only see this in new emerging industries. It's one of the first steps of a new industry's maturity."

Hughes said feuds among rival factions of a new industry are common and usually take a few years to shake out. Few attendees seem concerned by the schism between Bourquin and Curry.

"I'm just sitting here smiling (because Curry partner) Ron Bloom and Adam are the masters of generating publicity," said voice talent David Lawrence of The David Lawrence Show , who plans to roll out a service he'll offer to help local real estate agents create podcasts to sell houses. "How does this not amp up by 10-fold the attention to them, having an alternative site across the street and all that? They've already locked up many of the most-listened to podcasts and are the big dogs on the block. I don't know if this is real or manufactured, but it makes it all that much more interesting."

The main event looks to be a mix of serious business and socializing. Denver-based podcaster Paul Saurini of Barefoot Radio, for instance, is excited to meet colleagues after toiling for months on his own on his show, but he's also on the prowl for sponsors for his weekly comedy and music program that attracts more than 6,000 downloads per episode.

Saurini could be in luck. Several companies, including PodShow and Podtrac, will be looking to help connect talent with advertisers. Podtrac, in fact, rushed to get its system, which will be announced this weekend, finished in time for the conference.

Predictably, several podcasters will be recording their shows at the conference. In fact, Podcast Pickle directory owner Gary Leland has signed up 18 podcasters to do 20-minute versions of their show live at his booth, to be made available on Leland's site in one-hour blocks throughout the day.

And for many, the event is likely to feel like a mammoth meetup where this first generation of podcasters will actually put faces to voices and screen names. Dinners, poker games and even some romantic dates have been furiously arranged in recent weeks on message boards and via e-mail.