Orkut and Mixi

Recently, I was finally invited to join to Orkut and Mixi.
Mixi is, in a sense, Japanese version of Orkut.
There are at least two major differences between them.
One is that Orkut has "Community" but Mixi does not.
The other is that Mixi is rather "diary centric" design.
Of course, a user can put a URL in own profile page at Orkut, but Mixi asks what kinds of blog or diary system members use and checks their update by RSS!
Presumerbly, it's because Japanese people love making their diary be public and reading others so much.
Here, please don't ask me why Japanese do. :o)
In general, Japanese people tend to surpress to express their own opinion or thoughts.
In this sense, you might feel it's strange.
Here, I belive that they don't want to be silent but they just don't want to
ehave differently from others in company. This comes from cultural background
of Japan. As you can easily understand my point now, we can behave anonymously
in the Internet and that's why so much of Japanese love to express themselves
there."Community" of Orkut meanwhile doesn't seem to be functioning
as good as expected for me.
I think it has two aspects. That is, both encouraging participants to make
new friends and talk about partcular topics to their heart's content.
My point is that not so many communities are active, and I'm wondering
why they don't exploit that.
Do you have any idea?