The Japan Media Review has an article on A New Set of Social Rules for a Newly Wireless Society:

Keitai [cellphone]-wired youth are in persistent but lightweight contact with a small number of intimates, with whom they are expected to be available unless they are sleeping or working. Because of this portable, virtual peer space, the city is no longer a space of urban anonymity; even when out shopping, solo youths will send photos to friends of a pair of shoes they just bought, or send fast-breaking news about a hot sale that is just opening. After meeting face-to-face, a trail of text messages continues the conversation as friends disperse in trains, buses and on foot, nimble thumbs touch-typing on numeric keypads.