Blogging allows a community of learners to share ideas more quickly and efficiently.  It facilitates student/teacher and student/student interaction outside of the classroom more easily.  I envision students sharing their comments and questions on books, or activities, that they are reading, or working on, in school.  For some students that do not like to speak up in class as often, this will allow them the chance to properly word their comments and relieve some of the anxiety they might have with public speaking.  It seems like most of my students already spend a good portion of their time away from school on the computer, so why not combine something that they enjoy and already do with academics.