High school and college students generally do not have the home phone numbers of any but their closest friends. Before initiating a call to a keitai, they will, almost without exception, begin with a text message to determine availability; the new social norm is that you should "knock before entering." By sending messages like "Can you talk on the phone now?" or "Are you awake?" text messagers spare each other the rude awakening and disruption of a sudden phone call.

One teenage couple that participated in our study exchanged 30 text messages over the course of three hours as they watched television, ate dinner and did their homework, before engaging in a one-hour phone conversation. This voice contact was followed by another trail of 22 messages that kept them in contact until bedtime.

Keitai-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.

Just as Weblogs are distributing journalistic authority on the Internet, mobile media further de-centers information exchange by channeling it through networks that are persistently available to the mobile many.