Kathy Sierra over at Creating Passionate Users has a post entitled Can you teach someone to care? While it is isn't directly related to teaching or to blogging, the advice is applicable.
First of all, she makes the extremeley important statement that, "You usually can't create passionate users unless you deeply care about them." She then states, " Passion is infectious, and so is caring," and goes on to discuss how we can "infect" our colleagues and, I would hope, our institutions with this caring attitude by modeling it and by getting enough people on-board who care that the others start caring without really realizing it. (This is a very loose and quick summary of what she explains quite nicely. Read her post!)
The truth of thatfirst statement is pretty obvious, and yet we often miss it. If we want our students to care about our product (learning - English, in my case) and if we want them to be enthusiastic learners, we have to care about them. You would think that all teachers would care, but they obviously don't.
I also think this applies to getting our students to blog. Our passion for blogging - or for anything else - can be transmitted to our students. We have to share the passion with them, let them see it in our eyes and hear it in our voices. They will want to be involved. I have seen it time and time again with my own students.
Anyway, I recommend that you check out Kathy's post. And even more, I suggest you give her ideas some thought. Caring and passion -- I don't think we can teach without them!