(CNN) -- Jack Dorsey got the Twitter ball rolling, or chirping, on March 21, 2006.
"Just setting up my twttr," the co-founder of what's become a social media giant tweeted.
Some 1.653 million followers and five years later, Dorsey (@jack) returned this week to Twitter to become the company's executive chairman. He had stepped down as CEO in 2008.
Dorsey announced the news, suitably, on his Twitter account.
In his first television interview since resuming his duties, Dorsey led a cast of celebrities who appeared Tuesday on CNN's "Piers Morgan Tonight" (@PiersTonight) to discuss the continuing power of Twitter, home to 140 million tweets a day. Appearing with him was Twitter co-founder Biz Stone (@biz).
"It is extremely humbling to see quickly how the velocity of the service, how it has taken off," Dorsey told Morgan, himself a Twitter regular. "It gets faster and faster every day. Early on, we knew it was engaging, but we had no idea what people would do with it."
Guests on the show explained Twitter's impact on governments and celebrities. Among them:
-- Susan Rice, U.S. ambassador to the United Nations (@ambassadorRice), said Twitter "has dramatically changed the way people can communicate together, [to] rally one another to common objectives."
-- Home furnishings maven Martha Stewart (@MarthaStewart) said she uses Twitter to do consumer surveys, with results she can show to business partners.
-- For New York Times columnist Nicholas Kristof (@NickKristof), ignoring social media, including Twitter, "enormously raises the cost for repression for regimes. It holds dictators accountable."
-- Newark, New Jersey, Mayor Cory Booker (@CoryBooker) famously helped constituents during a huge snowstorm to hit the Eastern Seaboard by driving a snowplow and helping area residents, while tweeting along the way. "I was able to interact with people in a way we never had done before." Governments need to use such tools to better serve people, he said Tuesday.
-- Actress Alyssa Milano (@Alyssa_Milano) laughed about a Tweet she sent to the Old Spice deodorant guy and his video reply. Milano asked him to donate money to a charity. "Being able to raise money for causes important to me ... it is such a brilliant arena for that." She also announced the gender of her baby on Twitter.
There are, of course, some downsides to using Twitter and social media: Don't drink and tweet. Sending photos of your baby isn't for everyone. And beware if too much time on it affects personal relationships.
"I will continue to be a technology and social-media evangelist. But it's incumbent upon me to find a way to consume less -- and, more importantly, let it consume less of me," she wrote.
"It has an obsessive quality to it," Rosman told Morgan. "It's hard to create the boundaries."
Stone said early on he did not think the famous would be drawn to Twitter. "Celebrities and politicians realize they can have a connection with their fans they could not have anywhere else."
For their part, Dorsey and Stone are looking ways to further expand the service. Dorsey said Tuesday he wants Twitter to have more "mainstream relevancy," the Wall Street Journal reported.
Dorsey also is the creator and CEO of Square, an application that turns a smartphone into a mobile cash register.
Square uses a free download and plastic card reader to let users accept credit card payments.
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