My new professional project is heavily social media oriented and I need to know as much as possible about the japanese use of social media.
I found quite a lot about twitter (a good hint of how big it s becoming in japan)
- the diamond review 2010年ツイッターの旅
- the masato kogure book ツイッター 140文字が世界を変える
- the techcrunch article which disclosed that japan is now the 2nd largest twitter group with 14 percent of the tweets
I guess that s enough but if you have additionnal source of info....

In the other hand I didn t found anything very conclusive about mixi/facebook even if I do know that mixi is way more successful than facebook (about 17 million mixi users in japan , less than 2 million for facebook )and I read some analysis about the cultural problem raised by facebook . It falls short of expectation.

More than anything else I need data on the big three : gree/mixi/mobage town
anything about how it interacts with other networks/the behavior of users(time/money spent/content read/etc.)/type of users (age/sex/income/education/geographical position/etc.) of those 3 communities would be extremely precious

aside from those 3 :
yahoo days
cyworld
my space japan
amie
cafesta
my any
gocco
chibuya town
myMTV
mobarebo
rogotomo
nani suru
fans street
ixn
puchige friends

If i forgot a network, anything belonging to one of those 15 categories is relevant
Publish
Photo
Audio
Video
Microblogging
Livecasting
VirtualWorlds
Gaming
Aggregators
RSS
Search
Mobile
Interpersonal (Skype , acrobat connect, go to meeting)
"ProductivityApplications"(acteva ,eventful,monkey survey)

All I can find at the moment, one of which I posted previously, is: http://daisukeiizawa.com/resource/fbandMixi.pdf and http://nms.sagepub.com/cgi/content/abstr...09343462v1

I suppose at this point, "Personal, Portable, and Pedestrian" (ed. Mimi Ito) is mostly unrelated and too dated?

Also, I think from the same author as the latter article:

"The first of these talks about social network sites in an global context concerned the use of mobile phones and social network sites in Japan [1]. Toshie Takahashi, from Tokyo’s Rikkyo University, presented the results of two studies. The first were video interviews of Japanese youth on the streets of Tokyo. These interviews showed some of the passion that interviewees had for their mobile phones and how essential they felt they were to their day to day life. But most of the time in the talk and in the paper concerns the second study a comparison of Japanese young people’s take up of Japanese SNS Mixi with their use of MySpace. According to Takahashi, Mixi launched in Japan in 2004 and now has 15 million members. MySpace Japan launched only two years later, in 2006, and currently has 1.2 million users. Takahashi argued that the use of Mixi and MySpace reflected the tension in Japanese culture between the notion of Uchi and Soto. As she puts it in the paper, “Uchi (inside, us)...exists in the belonging of people to social groups linked by close interpersonal relationships.” This social intimacy is linked to strong social obligations. Soto corresponds to “outside, them” and is about an outward-facing presentation.

The details of her study are fascinating and I cannot cover many here (though the paper is online). Takahashi shows how people’s use of their MySpace accounts and their Mixi accounts are quite different in how they connect (or opt not to) with their friends and how they present themselves. There seems to be a different emotional valence in their use of each site, strongly connected with this tension between Uchi and Soto. Mixi opens up opportunities to be members of multiple Uchis (previously not thought possible), but this comes with significant social obligations to others. Use of MySpace, on the other hand, corresponds with the notion of Soto and people sometimes refuse connections to people they already know and rather present a radically different image of themselves as they connect to outside-Japan popular culture.

Takahashi concludes that contrary to the way a Senior Vice President at Viacom International Japan argued that Mixi is about “us” while MySpace Japan is really about “me, me, me,” both are about “me” and “them.” But Mixi is about “me and them” in Japan and involves a process of “re-Japanisation” while MySpace is about “me and them” in the global world and involves a romanticized process of self-creation and “de-Japanisation.” " - via

Asiajin.com has some articles with data on Mixi, Gree, Mobage-town, such as this one: http://asiajin.com/blog/2010/04/14/japan...n-members/