When M. gets home from school, he immediately logs on to his computer. Then he stays there, touching base with the people he has seen all day long, floating in a kind of multitasking heaven of communication. First, he clicks on his Web log, or blog -- an online diary he keeps on a Web site called LiveJournal -- and checks for responses from his readers. Next he reads his friends' journals, contributing his distinctive brand of wry, supportive commentary to their observations. Then he returns to his own journal to compose his entries: sometimes confessional, more often dry private...