Exactly six years ago Wednesday, Twitter co-founder Jack Dorsey published the first post on his new service Twttr. “Just setting up my twttr,” Dorsey wrote in his brief note. No one knew at the time, but his tweet was the first of trillions of messages that would be posted to the social networking service over the coming six years. Twitter has seen more than 532 million accounts registered in its six years, and the service is used around the world by people in all walks of life. While some still view Twitter as a wasteland packed with irrelevant minutiae, the service is also used by tens of millions of people and organizations as a means of communication and promotion. Twitter has even played an integral role for groups looking to organize in protest against oppressive regimes. Twitter announced on its blog Wednesday that the service is now home to more than 140 million active users who post an average of 340 million tweets per day. As of about a year ago, four months after Twitter celebrated its fifth birthday, the company confirmed that it was delivering an average of 350 million tweets each day.