A simple little technology has the digerati all atwitter.

Make that the twitterati. Twitter, a way to broadcast short text messages to large groups of people, is growing about 20 percent a week and in only seven months is already up to 60,000 users. More than a million messages, known as "twitters" to those in the know, have been sent out.

The technology, from small but cutting-edge Obvious Corp. in San Francisco's South Park neighborhood, has already attracted influential users such as presidential candidate John Edwards. Companies like MarketWatch.com, a part of Dow Jones, are sending alerts via Twitter. A host of jokesters, including people posing as Bill Clinton, Homer Simpson and Borat, have emerged on the service, offering up mock posts of their whereabouts.

Obvious was founded by Evan Williams, 34, who scored his first Internet hit when he founded Blogger, one of the first companies to make easy-to-use blogging software, and sold it to Google in 2003. With Obvious, Williams had been largely focused on Odeo, a podcasting technology, but when engineer Jack Dorsey, 30, came up with Twitter last year as a side project, the company ran with it.

The success is sort of shocking, considering that most information-overloaded people believe they have no desire to invite hundreds of new messages onto their cell phones. Yet once started, many people find Twitter strangely addictive, to say nothing of useful.

One question drives Twitter: "What are you doing?" Twitterers post answers to that whenever the mood strikes them. Every answer can have at most 140 characters. Twitters then get sent to friends, although any user can see virtually any other users' posts online, lending a voyeuristic thrill to the pastime.

Some sample twitters include:

-- "Riding my bicycle through the halls of the motel."

-- "At Ritual Coffee, the hand-crafted sign by the register now reads, 'Please, no blogging in line.' "

-- "Going to try on a tuxedo."

-- "I wonder if I get out from under the down comforter and take my PJ's off if my husband will read about it in the other room and join me ..."

The fake Bill Clinton posted, "Al Gore wins an Oscar .....WHOOPI DO....I was president of the United States for two terms....try and beat that you wheatgrass turkey!!"

The real John Edwards posted, "Community meeting on healthcare in Newton, IA. Then 1 1/2 hr drive to Burlington for a similar meeting. Later tonight, back in NC."

The folks from Obvious obsess on the question of "What are you doing?" They wear shirts that say "Wearing my Twitter shirt" and give out business cards that say, "Giving out my business card."

Add to that: "Working hard on numerous Twitter challenges." They have a long list of features they want to add, but first they need much bigger infrastructure to accommodate Twitter's growth. At peak times, the service is slow or even stopped.

They want to avoid the fate of Friendster, the classic example of a service that did not expand its computing power to meet its rapid growth in users, only to see most of the users flee, particularly to MySpace.

"At this stage, it drives me crazy every day," Williams said. "On the other hand, if you never have scaling problems, then you spent too much time optimizing before you launched. There's no fix. It's always incremental."

Twitter will also have to deal with competitors, including Dodgeball, a service that predates Twitter and that was acquired by Google in 2005. Although many twitterers at last week's South by Southwest Interactive Festival in Austin, Texas, said Dodgeball was more complicated to use, Williams conceded that Twitter's main function already exists, albeit hidden, in Dodgeball's Shoutout feature.

Robert Scoble, 42, who has achieved a certain renown for his Scobleizer blog and is now host of the online video blog the Scoble Show for San Mateo's PodTech, said he's heard from many people who can't stand the service. The flip side of that argument is that many people find Scoble's obsessive twittering annoying, as he estimates he posts 40 Twitters a day, and quite a few have removed him as a connection. He said he "spammed" John Edwards' BlackBerry.

Perhaps the greatest challenge will be finding a business model for Twitter. Obvious doesn't have one yet, but Williams isn't worried. He said he prefers to make sure he's built a great user experience first, and the business model will follow. "There's going to be some value if we can do it really well," he said.

Scoble concurred. "The world has taught me, if you have an audience, a business model will show up. Google demonstrated that. It was in business for four years before it found a business model," and now it's a multibillion-dollar company.

The model could be advertising, it could be selling Twitter as a service to companies, and it could find something else entirely.

Another risk for Twitter is the chance that it flames out. In a post, Chris Messina of South Park's Citizen Agency, asked, "After SXSW, will Twitter become the new popup?"

Williams can afford to be patient. He is looking to build Obvious itself on a business model that doesn't really exist yet. The company has 10 employees but is a key participant in the South Park community. It is among several companies experimenting with "co-working," in which it rents out empty desks to fledgling technologists, often finding synergies. It hosts a monthly Company Chow Fun, in which a dozen tech firms from the bustling neighborhood come in and brainstorm solutions to their problems.

Obvious will focus more on research and experimentation as it seeks to develop technology, rather than a venture capital-driven need to bring a hit to market, Williams said.

"That, to me, is a more fun way to develop products," he said.

Williams spent two years at Google after selling Blogger, bringing his friend Biz Stone, 33, from New York to work with him. But he left Google two years ago to start Odeo, and Stone joined him.

Odeo developed podcasting technology, and Williams says it has been neither a "clear failure or a huge success." Rather than fold the company, though, he scraped up about $2 million, paid the investors back and took complete control of it again.

He finished that deal in October. By then, Twitter was on its way, and he said this year that he would sell Odeo.

Dorsey, the engineer, developed Twitter early last year. He had been thinking of it since his time at the blog software firm LiveJournal, and when he showed it to his colleagues at Obvious, they loved it and started using it internally.

Stone came up with the name Twitter, which he said evokes birds -- in his words, "short bursts of information, something trivial. Everyone is chirping, having a good time, and their phones even twitter."

Originally they called it "twttr," but when it leaked out and grew in popularity, Stone says they "bought the vowels" and the domain name www.twitter.com.

Twitter terms

Here is some of the Twitter-related terminology we've overheard:

-- Twitterer: A user of Twitter.

-- Twittering: To send a Twitter message.

-- Twittermob: An unruly and ragtag horde of people who descend on an ill-prepared location after a provocative Twitter message.

-- Twittercal mass: A community that has achieved a critical mass of twitterers.

-- Twittermaps: A mashup technology that lets Twitter users find each other using Google maps.

-- Twitterrific and Twitteroo: Two services that let users post to Twitter using a Mac or PC.

-- Twitterpated: To be overwhelmed with Twitter messages.

-- Twitterrhea: The act of sending too many Twitter messages.

Source: Chronicle research