Interesting article. I also think this is down to the traditional Japanese separation of private and public (honne and tatamae – see http://en.wikipedia.org/wiki/Honne_and_tatemae). After all, social networking is basically managing your personal relationships on a public medium (I know most social networks have privacy controls, but most people either don’t know about them or don’t bother with them).
This may be more noticeable in the generations that grew-up without the internet or computers – I know a few 30-something Japanese who use social media a great deal, although I have no idea how many online friends they have.
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