Richard Florida did some analysis of the 500 most followed on Twitter, and discovered that most lived in the US, in Los Angeles and New York:
Richard Florida, Where the Twitterati Live
One explanation for America’s dominance is that it had a head start: Twitter was created and launched in the U.S. Most top U.S. accounts were registered earlier than those in other countries, and there is a clear relationship between how long an account has been active and how many followers it has accrued. It’s likely that American dominance will weaken somewhat as tweeters in other countries catch up. But that is clearly not the whole story.
And the use in Brazil is very interesting, and unexplained, here.
I think that the biggest reason for the United States’ dominance of Twitter is the fact that there is a high concentration of celebrities here. It’s no surprise to me that Los Angeles and New York are in first and second place, respectively, because that’s where they tend to live. The last paragraph of the article agrees.
Attention, it is often said, functions as an increasingly important currency in the post-industrial world. Between Hollywood and Madison Avenue, New York and Los Angeles are world capitals of celebrity and branding—it is only to be expected that they would dominate the twitterverse’s attention economy as well. It may not be the most finely calibrated gauge, but Twitter provides a revealing glimpse into our evolving cultural geography.