More than 60 percent of registered accounts come from outside the U.S., Matt Sanford, a lead engineer in Twitter's international team, wrote in a . According to a graph included in the post, the balance of Twitter accounts shifted to international users in about September last year.

Twitter is available in French, German, Italian, Japanese and Spanish. In some of those countries, growth happens when a politician or famous person starts using the service, Sanford wrote. For instance, in Columbia, sign-ups soared 300 percent after politician Piedad Cordoba Ruiz began using Twitter, he said. Politicians and Bollywood stars in India led to increased sign-ups in that country too.

At the recent CTIA conference, Twitter co-founder Biz Stone said the company hopes to offer the service in more languages. "We want Twitter to be available in as many languages as possible," he said.

Beyond offering the Twitter interface in local languages, he's been working to make Twitter easy to use on mobile phones in order to reach the many people around the world who don't have computers. Twitter has deals with 65 mobile operators that allow their users to send and receive tweets over SMS at no additional cost, he said.

"When a farmer in a rural village in a Third World nation can get the simplest of news over SMS, a weather report or whatever, it can have a dramatic impact," Stone said.