Twitter attracts about 1.9 million unique visitors a month. (Associated Press)

Guy Kawasaki has plenty of titles to choose from: author, venture capitalist and the chief executive of his own Web start-up, to name a few. But he has no illusions about what his real job has become: "I'm a professional Twitterer," Kawasaki says.

Throughout the day, the 54-year-old serial entrepreneur and former Apple marketing guru scours the Web for interesting links and siphons them into his Twitter feed in 140 characters or less, a stream of around 30 posts a day that flows into the accounts of more than 50,000 users. He peppers that collection of news, rumors and facts with references to his own site, Alltop.com, an aggregator of links to articles and blog posts on hundreds of subjects.

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"Around 99.9 per cent of Twitter users see it as something fun to do in your spare time, as some kind of nicety," Kawasaki adds. "I see it as a weapon."

The result of that focus, he says, is a steady flow of new users to Alltop — a site whose traffic has grown to 40 to 60 thousand page views a day in around eight months, according to Kawasaki's count.

Not every micro-blogger can leverage 140 character blurbs to grow a business. But Kawasaki holds a special distinction: By Forbes' calculation, he's the most influential Twitterer in the world. (Like many of the other top Twitters, Kawasaki also ranks prominently — ninth place — on our annual listing of the Internet's most famous people — the Web Celeb 25.)

To rank the influence of Twitter's micro-bloggers, we started with a list of the 30 most "followed" users, those whose microposts show up in the largest number of users' feeds. Then we weighted those rankings by the number of total "tweets" each users has posted and, equally important, the number of times those "tweets" have been "retweeted"— in other words, copied and reposted by other Twitter users.

Kawasaki has far fewer followers than other Twitter stars like Digg.com founder Kevin Rose, with more than 90,000 Twitter disciples, or tech pundit Leo Laporte, who has around 77,000 followers. (Barack Obama, whose Twitter feed has been silent since his election, has the most adherents of all with 144,000 followers.)

But more important, Kawasaki is the most "retweeted" user on the site: Over the past two months, his tweets have been reposted nearly 900 times, more than twice as often as the next-most retweeted user, according to data aggregated by independent social media consultant Dan Zarrella.

The real business benefits of that Twitter success are still largely a matter of faith: Kawasaki says that only 6 per cent of his Alltop traffic comes directly from Twitter, but he believes those social media users are more likely to become repeat visitors and pass the site on to their friends.

There's evidence to support that belief in Twitter's multiplying effect. Zarrella released the results of a survey in November showing that Twitter users have a penchant for redistributing content via other online media. They're slightly more likely than non-Twitterers to share new content on Facebook, twice as likely to post it on social media sites like Digg or Reddit, and about three times as likely to repost content in a blog, according to his study.

Twitter traffic up tenfold

Small though it may be now, Twitter's stream of eyeballs is also growing phenomenally fast: According to traffic counting firm ComScore, Twitter attracts about 1.9 million unique visitors a month, up tenfold from a year ago. And that number doesn't include Twitterers who access the service via cellphone or from desktop applications like Twhirl or Tweetdeck — potentially millions more users.

One key to grabbing that growing viral influence? Kawasaki suggests ignoring Twitter's initial "What are you doing?" prompt. Instead, he says, just post something interesting. "People want to read about how Microsoft is laying off 5,000 people or how doctors removed a 2.5 pound gallstone from a man's body," he says. "They don't want to read about how your cat rolled over or the length of the line at Starbucks."

'Asking a question leads to that flow-on effect of gaining new followers.'—Darren Rowse, blogger

Other Twitterati take different approaches. TechCrunch blogger Michael Arrington, who places fourth on our Twitter list, simply links to content from his network of influential tech blogs. Pete Cashmore, ranked sixth in Twitter influence, mixes links to his social media news site Mashable with more personal notes — earlier this month he expressed his doubts about a purported trend of Twittering during sex.

A less obvious technique for gaining a Twitter audience, says Darren Rowse, the seventh ranked Twitterer on our list, is simply asking questions. Influential users will likely respond publicly, putting your Twitter name in front of thousands of users who aren't yet following you.

"When they answer, it spurs their followers to engage with you as well," says Rowse, an Australian blogger who uses Twitter to promote his three sites, including Twitip.com, a blog devoted to Twitter's marketing potential. "Asking a question leads to that flow-on effect of gaining new followers."

Actor, blogger Wil Wheaton attracts 40,000 followers

But for some Twitter mavens, gaining fame on the micro-blogging platform isn't a matter of marketing tactics or media savvy so much as the unbidden expression of free-flowing geekery. Wil Wheaton, the teen actor who for years played the character Wesley Crusher on Star Trek, gained the 10th-place spot on our Twitter influence list by virtue of his lingering TV notoriety and a charismatic collection of posts on technology, video games, sports, and his personal life.

Wheaton, also an author and blogger, sees Twitter as a platform for instant communication with his followers, a kind of real-time hive mind. That personal approach has helped him attract more than 40,000 followers.

He disdains the idea that a crowd of attentive Web users could become an audience for marketing or branding tool. "Twitter offers instantaneous, simultaneous communication with potentially very large numbers of people," Wheaton says. "That sort of the thing has the potential to be exploited. But I think collective intelligence tends to see through marketing and advertising pretty quickly."

More interesting than Twitter's business potential, he says, is the kind of shared experience it can offer. Earlier this month, Wheaton was throwing a Frisbee with his son when he saw a meteor flash across the Southern Californian sky. He ran inside, noted the shooting star in his Twitter feed and immediately got responses from dozens of followers around the world who had spotted the same flash of burning space debris.

"That kind of thing," he says, "satisfies the geek in me tremendously."