David Marx has a great post up on the Clast blog, Shibuya-kei vs. Akiba-kei, where Marx not only explains the two subcultures but also explains why Akiba-kei is the dominant subculture of today’s Japan.
In the end, the Akiba-kei subculture has won a top spot in the contemporary pop landscape because its culture has been least affected by the last decade’s democratization of media and the decline in the culture markets. Shibuya-kei’s aesthetic sense now seems passé, but moreover, the media complex no longer has much use for that breed of cutting-edge indie culture engaged in obscure international art and music. Insularity is not just limited to Akiba-kei in contemporary Japan, but defines the youth generation as a whole.
Apologies- my comments are broken again. Working on it when I have the time.