Because he wanted to focus on making the service mobile, he applied his knowledge of short-message service (SMS) text, thus requiring users to render a Twitter update in 140 characters or less.

"It's only useful if it's short, and you have more or less one line to say what you're doing," Dorsey said. "And that concept in general just allows you to be a little bit freer. [E-mail] is like being presented with this massive white canvas, versus something [like Twitter] that is postcard size. It's less intimidating."

But Twitter, which has taken a few rounds of funding, hasn't been without problems, not the least of which it hasn't found a way to make money. Scaling for a growing user base has also been a problem. Users have at times been unable to send a tweet (a message on Twitter) or read replies to their tweets from friends.

A pop-up saying, "Twitter is stressing a bit" has become a frequent error message. On June 30, for instance, some users who logged in to the service received an error message that Twitter.com's server wasn't responding and the network had timed out. Since February of last year, some reports have estimated that Twitter has been down for nine days or more.

Also, it's not clear that Twitter has hit the kind of mainstream adoption that other social networking services, such as Facebook, have enjoyed, making the technology a harder leap for those in the business environment.

"It's still pretty much early adopters and people who are interested in social media," says Jeremiah Owyang, a senior analyst with Forrester Research who examines social technologies.

In fact, last October, Forrester issued a report that estimated, on average, 78 percent of Twitter's audience is male, 31 years old and draws an annual income of $78,000. This group, the report went on, was predisposed to using new technologies, especially those of the Web 2.0 variety, such as desktop widgets, tagging and wikis.

But lately there have been signs that Twitter is catching on mainstream. Staff members of both Senator Barack Obama of Illinois and John McCain of Arizona have used Twitter to debate the issues of their presidential contest (probably more concisely than in a town hall meeting), and the Los Angeles Fire Department utilized the tool to publish short updates regarding the California wildfires in 2007.

Catching the Eyes of Business Users

Twitter has also led business executives and managers to think about how they might take advantage of the service to improve and streamline internal communications. Drewe Zanki works for Rio Tinto, a British mining company and oversees an IT group in its minerals division in Denver. He heard about Twitter by reading some of his favorite blogs and immediately became interested. He joined just a few weeks ago.