When it comes to classroom blogging, I am an advocate of a program that:
begins with a class blog before allowing students to work on their own blogs
is integrated into a literacy program on a regular basis (while incorporating other curriculum areas)
sets high standards for writing, design, netiquette etc.
is regularly maintained and is an evolving space
allows students to express themselves while improving their educational outcomes
provides feedback and explicit teaching to students
begins with a high level of teacher guidance, before increasingly offering students more responsibility.