Thierry de Baillon wrote an article about Japan and social media acceptance, which I thought I'd comment on.
I agree that Social Networking Service acceptance, or lack thereof, is not a simple matter of Japanese being "shy". Just go to Shibuya, Harajuku, or Kabukicho to prove otherwise! I think SNS acceptance is driven by the marketing of the SNS, by whether it "feels right" and "fits right" for Japanese people, and by whether other people are using it. I think that's what Thierry is saying anyway, but my perspective is that SNS's like Mixi are Japanese to begin with and not a localized version of an application like Facebook or MySpace.
Take Mixi: it's Japanese to begin with, so there were no strange hurdles to overcome; it's a bespoke system for Japanese by Japanese. I know a lot of localized applications that were not designed with Japanese in mind, from the language used in the user interface, to the UI layout and its functions, to the way the application was marketed.
Twitter's simple, and it's really easy to explain to people, whether they agree that they would like to participate in what Twitter offers. However, other apps that are more complex, would require quite a bit more explanation and "selling." If something needs selling like that, the sales process in itself is a barrier to adoption, not to mention other barriers like poor Japanese documentation, search that does not work in Japanese, or functional concepts that don't fit Japanese cultural concepts like "amae" which Thierry mentioned.
If you look at who first pushed Twitter here - Digital Garage - it says a lot. One thing that the Japanese joke about often is, their propensity to do things that either thought leaders or, "everyone else" is doing. The Japanese saying that describes this is:
Akashingo wo minna de watareba, kowakunai!
If everyone crosses at the red light, there's nothing to fear!
If Japanese discover something that "everyone else" is doing, many will do it just to see what it's like, whether it makes sense or not. If on the other hand they hear something is "strange" or "a pain" they'll be reluctant to even try. Anyway, that's my two yen on SNS adoption.
