NEW YORK (CNNMoney) -- Five years ago today, Twitter cofounder Jack Dorsey blasted off the very first tweet. What began as an experiment in "microblogging" -- no more than 140 characters, please -- has become a cultural landmark.
Twitter now has 200 million users, including tech luminaries, celebrities and the president of the United States. It started off slowly: In 2007, Twitter averaged just 5,000 tweets per day. But in 2009, the site hit a tipping point and became a broadcast channel for major news events.
The now-iconic photo of passengers lined up on the wings of the plane Capt. Chesley "Sully" Sullenberger landed in the Hudson River went out to the world on Twitter (from @jkrums: "There's a plane in the Hudson. I'm on the ferry going to pick up the people. Crazy."). Six months later, during Michael Jackson's funeral, users blasted off 456 tweets per second -- a site record at the time. Now, those numbers look quaint: Twitter currently fields 140 million tweets in a typical day, or more than 1,600 every second.
The site's most dramatic moments have come during political uprisings. In Moldova, Iran, Tunisia and Egypt, protestors turned the site into a communications hub, using it to coordinate plans and broadcast their message. The U.S. State Department spotlighted Twitter's growing role in global statecraft when, during the Iranian election protests, it asked the company to delay planned maintenance and keep its network running.
"I've had a career-long interest in this democratization of information, getting people to express themselves, especially places where they wouldn't have a voice," co-founder Biz Stone told CNNMoney in an interview last year.
Exponential expansion comes with growing pains. Twitter's "Fail Whale" mascot became famous thanks to frequent appearances as the site's infrastructure struggled to keep up with usage spikes.
The company has been through two management shakeups. The first, in 2008, had co-founder Evan Williams take over from Dorsey as CEO; the second, five months ago, moved then-COO Dick Costolo into the top spot.
He's got a daunting challenge: Turn Twitter into a business. The site now has 400 employees and raised an eye-popping $360 million from investors, but has generated scant revenue.
If it wants to survive another five years, it needs to turn tweets into profits. Search engines like Google and Microsoft's Bing pay Twitter for access to its "firehose" of real-time tweet data; advertising is another revenue stream. Costolo's job is to find enough moneymakers to justify Twitter's $4 billion valuation.
Twitter's earliest pioneers have moved on. Jack Dorsey is now working on building a mobile payment platform at his new company, Square. After helming a big redesign last summer, Evan Williams is taking an extended break from day-to-day Twitter involvement.
But Dorsey says that whatever happens next for Twitter, it's already established a legacy and changed how we communicate online.
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