Advertising will not serve as the basis of a revenue model for Twitter, according to Biz Stone, co-founder of the rapidly-growing microblogging service.

According to a Reuters story, Twitter is developing several tools and services geared to business and professional users, items that could form the basis of a future revenue stream.

Despite its popularity, Twitter produces no profits for its investors. Stone told the Reuters Global Technology Summit yesterday the company was under no immediate pressure to do so, but acknowledged that a revenue model would have to be determined eventually.

However, he dismissed the idea of opening up Twitter to advertisers, telling the summit attendees that ads would irritate users and that Twitter does not have the required expertise among its 40-person staff.

“There are no people at Twitter who know anything about advertising or work in advertising. So we don’t have anyone there to make or take those calls,” said Stone, who added that the San Francisco-based company planned to double its head count by the end of the year.

Stone floated the idea of charging for new analytics and directory services, and said the company had spoken with mobile phone carriers about possible revenue-sharing agreements, but said Twitter would remain fundamentally free for consumers and businesses.

The quest to discover a revenue stream for Twitter has become a topic of much fascination in the business community, particularly among social media experts.

“This is like the game of the week—how is Twitter going to make money before they burn through their VC funding?” said Maggie Fox, founder and CEO of Social Media Group.

Like Stone, Fox believes that Twitter’s profit potential lies in technical innovation, not advertising.

“Most people don’t go to Twitter.com to interact with it. They use things like Tweetdeck,” said Fox. “So what has happened is that most of the value and activity takes place in the ecosystem around Twitter, rather than Twitter.com. Even if they had advertising on Twitter.com, most people don’t interact with the site that way.

“To me, the opportunity to make money is in leveraging those third-party applications [like Tweetdeck],” she said.

Business people who are heavy Twitter users might be willing to pay “$30 or $40 a month” for a tool that lets them share an account effectively with their employees and coworkers, said Fox.

“If you’re a super-user or someone with a reason to want to use it very heavily, if you can make it easier and more efficient, that’s a very clear value proposition.”

Michael Tippett, co-founder of the Vancouver-based NowPublic Technologies—which created the citizen journalism website NowPublic.com—believes that Twitter can generate profit from its value as an information provider.

“From a news perspective, it’s hugely valuable. It’s what organizations like the Associated Press and traditional news organizations are trying to deliver, and they’re delivering that in 140-character snippets,” said Tippett.

“Intrinsically, it has huge value, and where Twitter will end up making their money is through partnerships with organizations that tap into that universe of data and help make sense of it.”

Reuters reported that Twitter turned down a $500 million purchase offer from Facebook last year.