Mizuko Ito, apparently the sister of Joi Ito, has written an insightful article on new social behaviors among youth in Japan enabled by the mobile phone, and Vodafone has published it on their website.

Some quotes:

Now that mobile phones have become a norm for youths in Japan as elsewhere, distant others are always socially co-present, and place — where you locate yourself — has become a hybrid relation between physical and wirelessly co-present context.

and

In most of the gatherings we saw between heavy mobile email users, a trail of messages were scattered after a physical gathering as people continued the conversation, mentioned a forgotten bit of information, or gave thanks to the person who organized the gathering... The new norm is that these exchanges happen as people scatter to return home on foot or public transport. The dead time in transit on the way home is now occupied by the fading embers of conversation and contact.

Not too much of a surprise, except that in her research, she definitely found new social norms emerging that are mostly incomprehensible to the older generation that grew up without the technology.