Serkan Toto wrote a very good article about SNS and Japanese market (Taking social network abroad - Why MySpace and Facebook are failing in Japan).
This is very relevant to me because my company has just launched a brand-new social networking application for iPhone users (Big Canvas PhotoShare, available at Tunes App Store).
In a nut shell, Big Canvas PhotoShare is a photo version of Twitter, strictly targeting iPhone users who essentially carry "always-connected camera".
We strongly believe that Apple's iPhone is the first generation of devices that enable true "always-connected" lifestyle.
It is so obviously to me that the "visual communication" will be the next wave of communication after voice and text (phone calls and SMS), and we have designed PhotoShare from scratch to optimize it for those people who would really enjoy always-connected lifestyle enabled by iPhone.
Thanks to Apple's App Store (which allows us to release our applications without having any negotiation with wireless operators), we have released PhotoShare to 30 countries at the day one Apple opened the App Store.
Within a few weeks, we've got thousands of very active users from all over the world (US, Canada, Japan, Hong Kong, Holland, Greek, ...) posting their photos daily and communicating over those photos. As far as I remember, I saw titles and comments in English, Japanese, Russian, Korean, Chinese, French and Spanish.
As I have expected, Asian users, especially Japanese users (who are much more familiar with this "always-connected" lifestyle because of DoCoMo's i-mode) are using PhotoShare much more actively and effectively, posting their daily activities, including lunches they had, restaurants they went, fireworks they say, and parties they went, while many American users are still using it as if this is a iPhone version of Flickr or MySpace.
As the result, I see a lot of photos posted by Japanese users than American users (despite the larger number of American users). It concerned me a little bit at the beginning, but my concern is a lot less because many American users started realizing the fact that PhotoShare is very different from Flickr, and it is a tool to share their daily experience with others (either privately or publicly).
As Serkan has pointed out in his article, building a true world-wide social networking service is not easy because of the language barrier and the cultural barrier. Luckily, photo-based communication reduced the language barrier significantly, and I see some evidence. The difference in culture is much more challenging, but I am hoping that it would be relatively easy for text-message generation of Americans users to adapt Japanese-style "always-connected" lifestyle.
There are still a lot of things we need to do to make PhotoShare a true world-wide social network service, but It would be really great if we are able to bridge the gaps among multiple languages and cultures, which even MySpace and Facebook are having a hard time to deal with.