Mobile usage in Japan is among the highest in the world, with over 90% of the population using mobile devices.  More than 90% of these users have mobile data plans, which are commonly 3G-enabled.  And while 75% of these mobile internet users are tapping into “social networking” sites from their phones, the top app being used isn’t Facebook, Twitter or even MySpace.  It’s a Japan-based social networking site called mixi

Founded in 2004, mixi has more than 21.6 million users, which accounts for roughly 80% of the social networking market in Japan.  For the past three years, mixi has been working to create the largest online Christmas event. This year’s event, called mixi Xmas 2011, enables mixi users to sign up to share holiday messages and send virtual gifts or online coupons  to one another.

This year’s event started in November and by the second day of the campaign, active users exceeded one million with more than 2.5 regular active users regularly participating. 

Organizers credit a large part of their success to the use of Windows Azure and the Content Delivery Network (CDN), which has given them the ability to scale resources dynamically in response to spikes in usage and traffic. 

Read more about this story in the press release (translated from Japanese), or read the original Japanese version here