Happy 6th Birthday, Twitter!

March 21, 2012— -- "Just setting up my twttr," Twitter co-founder Jack Dorsey sent from a service that no one had heard of exactly six years ago. It was the first tweet, or 140-character message, to ever be sent on Twitter.

Twitter hasn't changed all that much since Dorsey fired off that tweet at 3:50PM on March 21, 2006. However, while the format is the same -- 140 characters to make a statement, hashtags used to sort by topic, and an @ symbol attached to a username – the service has changed the way millions of people consume information, share and communicate.

"It's really been about how people have changed around the platform and they've gotten very used to conversing in these short text bursts," says Mashable editor-in-chief Lance Ulanoff, who uses Twitter daily. He says people are turning to Twitter first as a way to get their news out.

"It's become incredibly important in people's lives to share information first with their audience, with their friends, you know, people they've never met before, but it's just become a truly powerful platform."

Powerful, indeed. Once criticized as a place where people go to share what they ate for breakfast, the micro-blogging site is now the first place many people go to get their news.

Tech evangelist Robert Scoble tells ABC News Twitter has become part of our media diet. "I don't see it going away, I see it becoming more and more important."

Think about that famous picture of Captain Chesley Sullenberger's US Airways plane landing on the Hudson River. It appeared first on Twitter.

And what about the Arab Spring? A 2011 study from the University of Washington says Twitter and other social media sites played a central role leading up to the toppling of the Tunisian and Egyptian dictators. Turns out Twitter is a great way to organize a revolution.

And the death of Osama bin Laden? If you were on Twitter, you knew about it before President Obama gave his televised address to the nation.

And then-candidate Barack Obama certainly wasn't the first politician to use social media on the campaign trail, but he was the first to realize and harness the money-raising powers of Twitter and other social networks. His followers were kept updated on his progress and when he won the presidency, he tweeted: "We just made history. All of this happened because you gave your time, talent and passion. All of this happened because of you. Thanks."

Since then, politicians have taken to Twitter to reach their constituents and get their message out.

"Politicians understand that if people feel like these tweets are coming directly from them, they may be able to understand the politician a little bit better and they certainly feel like they have a more direct connection, or a more personal connection to these people," says Ulanoff.

About a year ago, Twitter was valued at about $10 billion, while it struggled to explain its business model to people.Now it's firmly planted in the world of advertising and is using promoted tweets as a way to make money, bring in $139 million last year in ad revenue.

Scoble says there's "a number of different ways to make money but the top one is going to be advertising."

Twitter has used cash from a round of private investment funding last year (there's talk of a public share offer at some point) to invest in services and talent. Most recently it bought Posterous, a micro-blogging service, similar to Tumblr.

The company hasn't revealed what it intends to do with the service, but Gartner research director Michael Gartenberg says, "It appears Twitter is looking to evolve from the status update service it started as to an information service optimized for sharing and consuming information and content."

Based on that, maybe in its sixth year Twitter might see its biggest changes.