There is a lot of hype and hope in the U.S. around taking social networks mobile, but mobile social networking is still in the fledgling stages in the West. In Japan, it is already a reality. One company in particular, DeNA, has taken Japan by storm with its mobile SNS/virtual world/gaming platform Mobage-town. DeNA opened a US office in San Mateo earlier this year, with plans to offer an English version of Mobage-town this fall.

Subscribers can exchange messages, chat in communities, share music, read pocket novels, and blog, among other things. The site’s “killer feature”, however, is the vast selection of free games that makes most users register in the first place.

Each of the 11 million Mobage-town members is represented by an avatar “living” in a virtual room. Both the characters and rooms can be pimped out with new clothes and wallpaper, for example. In order to do that, users must acquire “Moba Gold”, a virtual currency established by DeNA, by clicking on ads, signing up for affiliate services and inviting new members.

The circular business model has paid off for the company, which is listed on the Tokyo stock exchange (market cap: $2.3 billion). Mobage-town alone raked in $46 million in sales in the first quarter of this year and saw nearly 15 billion page views in June. And yes, this is Japan- and mobile-only.