Found thanks to @skyboub a great financial expert of the valley, Twitter's traffic has more than doubled last year. This is not that surprising to see one of the hypest social media having such a fast growth pace, but what is very interesting as @skyboub said, is that Twitter has Twitter, with almost as many single users coming from Europe (100% growth) vs USA (20%).
Hence, if we analyse this chart, we can see that the Northen American market is near to be mature. With a worlwide growth of 109% compared to 22% in the United States, we can see that the US and Canada is already pretty big users of the service. 25 million users for about 310 million Canadian/US Citizens, we may say that 8% of the population of North America are Twitter users (unique users that connected at least once in the month of June 2010).
Hence, Twitter's worldwide growth is supported by Europe, but also other emerging continents like Latin America or Asia. But I'd really like to know how did Twitter has managed to cross borders and hence, to get such a large impact on other continents. Did they advertize? Did they have PR?
Indonesia had the highest penetration of Twitter usage, comScore’s data showed, with more than 20 percent of Internet users in that country visiting the website in June, followed by Brazil and Venezuela with 20 percent and 19 percent respectively. Venezuela’s adoption of the service could have been driven in part by Venezuelan President Hugo Chavez’s decision to join Twitter in late April, comScore said.
Now Twitter is big, and as I have said already, they must rush now to get a business modell in order to monetize their large audience.