Twitter Diffusion ~ Accelerating US Adoption...

US Twitter Adoption map over time...

"From late March 2006 through the early August 2009, nearly 3.5 million people signed up for twitter. 2.3 million of those users signed up in the 408 cities displayed here. As users sign up, the blue circles grow and size and turn read then that city reaches a critical mass of users. We defined critical mass as achieving 13.5% of the total number of users that city will gain over the three years. The graph represents the number of new users signing up each week."

Definitely read Traditional social networks fueled Twitter’s spread...

"...the site’s growth in the United States actually relied primarily on media attention and traditional social networks based on geographic proximity and socioeconomic similarity"