Can you change the world in 140 characters? That's the challenge facing Biz Stone, co-founder of Twitter, the microblogging website where users answer the question "What are you doing?" in a dozen or so words. It's harder than it looks. The sentence you're reading now contains 180 characters (including punctuation and spaces), too long to be a complete tweet, the term used to describe a post on the Twitter site.

It's hard to gauge just how large the Twitterverse is. Although Twitter's user base has increased 600 percent over the past 12 months, and the Wall Street Journal recently declared that the site had gone "mainstream," the tight-lipped, privately held company refuses to disclose its total number of users, or the number of tweets sent daily. But most "tweeps" who use the service are all too familiar with the "fail whale" page that appears when heavy traffic brings the site to screeching to a halt.

Riding this rocket requires Stone to spend much of his time on the road, spreading the word to those who still think Twitter is the sound a bird makes. "Most tech folks already know about us," he says. "So now we go to others, trying to grow the network. The information industry, the newspaper industry."

He recently traveled to Boulder, Colorado, to explain the service to executives at the advertising agency Crispin Porter & Bogusky, and to Los Angeles to meet with the creative folks at talent firm Creative Artists Agency. After speaking at the Haas School of Business at Berkeley, he chatted up a professor about Twitter's role in the marketing world. The next day she had her students use the site's search engine to explore how people were using it to discuss certain brands. "They were stunned to find people twittering about everything from Borax to Monster Energy Drinks," he says.

Today, Stone is on the road about once a month, down from two or three times a month. The change was a deliberate decision. "Last year was crazy. I was going to L.A., Boston, Europe," he says. "It was tiring. So I've made an effort to say no to as many things as possible."

Still, he adds, it's important to occasionally meet up with someone and grab a cup of coffee. "Stuff comes out when you meet face-to-face, bursts of information."

Stone learned the value of getting out of the office back in the mid-'90s. As a book-jacket designer for Little Brown and Company in Boston, he and art director Steve Snider would drive to New York to present design ideas to execs at Little Brown's parent company Time Warner. Those three-and-a-half-hour car rides were enjoyable-and productive. "We'd discuss design ideas, write screenplays, all sorts of things," Stone recalls. "Steve and I are still very good friends, and we often talk about how we miss those car rides."

After Twitter acquired the small search company Summize earlier this year, he traveled to New York to meet the team. He'd already conversed with them by phone and email, but says that, in person, they blew him away with their demeanor, intelligence, and attitude.

"The meeting helped me understand what a perfect match the two companies made," he explains.

Like most road warriors, Stone is ambivalent about the experience. "Do I enjoy it?" he asks. "Yes and no. I'm the type of guy who never takes a vacation, so when I go somewhere on business, I often try to combine the trip with visiting friends. When I recently went to Colorado, I stayed with some friends I grew up with who just happened to all end up in Boulder."

He's also proud to be a notoriously light traveler. "People are constantly asking me, 'Is that all you brought?'" he says of the half-size backpack that he carries. "I travel with my iPhone, my MacBook Air, a few black T-shirts, jeans, and some clean socks and underwear. That's it. If I need something else, I'll buy it. It's not worth it to have to worry about a big piece of luggage."

Stone likes to stay light during the day too, leaving his laptop at his hotel and doing virtually all his computing by smartphone. "Unless I've really got a lot of typing to do, I use my iPhone instead. I'm pretty good with the virtual keypad. I can type with my thumbs or with two fingers if the phone's on a table. It sounds crazy, but it works for me."

Especially since he's usually typing no more than 140 characters at a time.

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