From what I heard (but I am no expert at all) Japanese culture encourages an extremely sharp (at least from the standpoint of Europeans and I would guess Americans) separation between business and private life, e.g. behavior which Europeans would consider highly eccentric - say a high powered banker running around disguised as Mickey Mouse in his off time - are considered a non issue.

In case this is true, this could be a reason why Japanese people don't really see much of a need to ensure that an online identity can be traced to "real identity", because they consider the "virtual identity" to be "good/real enough".

Maybe there's a market for a social networking site that let's one maintain sets of identities, segregated (or joined) by groups or "circles" of people from different facets of their life?

I know we often talk about separate facebook accounts for work/regular life people, but why not for online identities as well?

FB doesn't allow this (nor do any other social networking site I'm aware of)...

Google Circles was supposed to do this, but it turned out that the entire product was a misunderstanding.

A better way to maintain private circles is through closed Facebook groups.

If you want to go one step farther and talk freely/anonymously among friends and colleagues, see my comment below. I am working on a startup that does just that.

okcupid works like mixi in this way (and a lot of other ways, too). It's a shame that they call themselves a dating site; they're really a social network for people who met online.

I would love to see those guys pivot, and release a multi-identity facebook killer.

Not that they need to (I think they are bootstrapped), but it would be cool.

They also just got acquired by match.com, so probably not happening.

Well, I hope they can vest soon.

That only works as long as the segregation is securely maintained. The risk of hacks, subpoenas, or employee misbehavior is too high to make such a system trustworthy, in my mind at least.

The best and simplest way is to simply maintain separate accounts, such that the separation is enforced in your head.

Appleseed and The Diaspora project both have "life-aspect" separation as explicit goals.

Closest thing I know of is Ning.

pseudonyms for artists are pretty well established, but most people on facebook don't create anything.

they're just ordinary folk wanting to connect, e.g. as they did with the new tech of the phone.

Interesting. Is this a privacy concern or just something intrinsic people do in Japan online?

(somebody stop me if I'm completely off-base)

It's been my observation that Japanese culture appears to be more accepting of and comfortable with people putting on personas to suit a particular mileu than in the west.

In the West we strongly equate what a person is wearing and their behavior at that moment with their overall identity. It's been my observation that in Japan a person may put on a persona like one might put on a costume and it be perfectly acceptable.

There's exceptions of course but nothing is more disconcerting to me as a westerner, watching an interview with a Japanese Rock and Roller or Rapper, expecting them to have the FU attitude I'm used to seeing during the interview and instead see them behave with politeness, nicely bowing at the right moments and talking politely to everyone.

It's actually quite refreshing in a sense to see this and I think it can encourage experimentation as it prevents people from getting too wrapped up with a persona they are building right now and drop it and try something else that suits their fancy.

This could be due to the strong emphasis Western culture places on "integrity." This term originally comes from the same Latin root as "integer," which itself means "whole, entire." Having integrity implies that your private self and public self are one and the same.

Multicultural roots of Western culture may have made integrity an important signifier of trustworthiness. Even going back to Shakespeare, you saw the theme of split identities everywhere in Western literature, and most of Shakespeare's villains are noted for their two-facedness.

The modern day implication of that cultural legacy is our cult of authenticity. For a rap singer to be taken seriously by his peers, he has to be "real." The realness is a hard earned credibility by showing a singular identity, and not being perceived as the real thing for someone immersed in that culture would be the equivalent of "losing face" in Eastern cultures. Something akin to social isolation and even death.

Another, perhaps more relatable example, is something I often hear Americans say. It's said that in America you can be who you say you are. That is at the heart of the open society for which Americans are praised, and Americans take your word at face value, until you say or do something contrary to their expectations of your self-proclaimed "role."

So thinking over what I wrote, I think the reason why role-playing works in Japan and doesn't in America is because Americans have a culture of self-invention, a culture built on appearances, they also have a wariness about being taken in by people who change their appearances often.

Not intrinsic to Japan as the OP noted, but it comes naturally to people. Zuckerberg's stance is mostly motivated by earning money off peddling Facebook.

Mostly? I would say entirely. It's funny when someone keeps doing something people hate over and over for money and then eventually develop a "vision" that allows them to keep doing the same thing.