How to use a blog?

I don't believe it is possible to make an a priori decision about the uses of a blog for a particular group of students. Testing it in practice is likely to produce different results with different students. I say this from experience. I use an online class journal with one group of students: this is not technically a blog (and is in fact based around google documents) but it shares many salient features with a blog. About half the class really enjoy it and find it a useful way of extending their use of English outside the classroom, a quarter occasionally use it, and a quarter more or less don't bother - or require firm prompting. For me this is neither surprising nor disappointing. Next term I will continue with the experiment. I am trying to test different ways of giving feedback - either commenting only on the content, or including comments on their language.