Who knew six years ago today, a little-known startup called Twitter (News - Alert) would turn into the biggest micro-blogging and social platform on the planet?

This time last year, Twitter announced more than 200 million people had signed up for the service. Today, some estimates put that number closer to 500 million total Twitter accounts.

It was March 21, 2006 when Jack Dorsey sent out the first tweet, “just setting up my twttr.” Dorsey (@Jack) is the current executive chairman of Twitter and CEO of another startup called Square. Just over three years after his groundbreaking tweet, Twitter reached a milestone of one billion tweets.

Twitter processes about 250 million tweets per day, according to statistics from October, 2011. The craze has sparked an interest in combining broadcast television and social networking. MTV, VH1, Bravo, E! and events like the Super Bowl integrate live Twitter streaming during broadcasts. Combining the Internet, social media and broadcast television is surely the wave of the future.

eMarketer (News - Alert) estimates the network will produce $260 million in ad revenue this year, Much of which will pay off Twitter’s growing expense sheet, including a workforce that has doubled since last year to 900 employees. According to Gawker, Twitter has actually lost money the past few years. In 2010, Twitter posted a net loss of $67.8 million.

Despite financial woes of the six-year-old company, eMarketer estimates Twitter’s revenue stream will increase steadily to $540 million in 2014. Twitter continues to grow after adding new languages to its platform, as well as acquiring the blogging software maker, Posterous (News - Alert).

Twitter certainly made an impact in the world its first six years, including a role in presidential elections, breaking news, social marketing and connecting people from around the globe.