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The digital revolution promised us that the nation state would wither away. But the spread of social networks show that however much the Internet connects us, quirks divide us. Take, for example, the inexplicable popularity of Twitter in Japan. Tokyo out-tweets New York and San Francisco combined. Pingdom, a website analyst, finds that Twitter is more intensely popular in Japan than in the United States. The conventional theories — Japan's high wireless usage, for example — fail to explain it.

Joi Ito, an early Twitter user and an investor who helped launch the service's Japanese version, said in April that the wireless theory doesn't apply. Early on, Japanese users were 30 percent of the service's base, a percentage that has fallen as it has grown in the U.S. and elsewhere. But they used the site despite its flaws. Though Japan has long been text-message crazy, Twitter didn't have a Japanese SMS service at first. Even entering a message in Japanese characters required a workaround.

Ito thinks that Twitter's simplicity struck an emotional chord in the famously minimalist country:

It got crazy early adoption in Japan from the beginning. One of my theories is that a lot of services in Japan to be either closed or over-featured portals and simple services with good open APIs are not as common as in the US and it attracts developers and users who are sort of sick of a lot of the bloaty Japanese services.

Here's another theory on why Twitter spread: Ito himself. Though he's too modest to say it, the globetrotting venture capitalist is a key bridge between San Francisco and Tokyo. Could it be that Twitter spread in Japan in part because Ito, Web 2.0's trans-Pacific import-export specialist, took note of it, and others followed the trendspotter? We are talking about a social network, after all. People may stay because of their features, but they join because of their friends.

As late as last year, Ito was hedging his bets, favoring Twitter rival Jaiku in April 2007: "I've been helping the Jaiku guys out a bit as an advisor and I'm also a friend of Ev's." (That's Ev Williams, Twitter's founder.) Less than a year later, Jaiku had been sold to Google, and Ito announced he was investing in Twitter. It's not an explanation that coders will like, but Twitter's spread in Japan suggests success really does come down to who you know.

(Chart by Pingdom)