Introduction to Blogs

This week in class we were introduced to the class and we discussed blogs. The purpose of our blogs will be to comment or reflect on experiences we have in class each week.
We also discussed our class online discussion board, which we will use to comment on class topics, ask questions of each other, and hopefully be able to help each other with issues we may have.
While I am new to blogging, it seems to me that a blog will be a great tool for us as students currently, and will be a great tool when we are teachers ourselves. A blog could be used as a site for parents of our students. They would be able to log in and see what we are doing in class on a given day/week/unit. Depending on the age of the students we are teaching, a blog could be used for them to post their own thoughts in an online journal. They would be able to interact with each other and comment on each others' ideas. It may be a resource for them to give comments on homework assignments as well.
I do wonder how many children use or have their own blogs. At what age does this become an appropriate learning tool for them?