I am about to begin blogging with my students. I have given out the guidelines and the rubric for grading their responses and questions. DO I post a question and allow students to respond to me and each other, or do I allow the students to form the questions and they post to answer each other questions?
I don't know how much research you have done about guidelines for you district about using blogs for educational use. I teach in Anne Arundel County and there are specific rules about using blogs with your students. You have to take a class before you are able to use this type of technology. I just wanted to give you a heads up because recently teachers in my school have been reprimanded for not following protocol.
Yes, that's a very important point! Another point would be that you wouldn't want to start a project with a number of learners who'll invest considerable time and effort, only to have it cut short when management discovers it.
There are a lot of concerns about web privacy and safety that need to be addressed as well and even some awareness training programmes may be out of date already. Here's an article I co-authored a few weeks ago: http://blog.matbury.com/2011/12/11/a-thorny-issue-protecting-teache... but it's well worth doing more research for more recent developments.
Self-hosting is an easier option than most people seem to think. If your school already has a website, it'd be easy for IT support to install some software free open source software for such projects. It may be a bit of hassle to get permission and set it up in the first place, but once it's been tried and tested, there'll be a lot more support for it and you can share it with other teachers. Who knows, you might win awards, get invited to present at conferences and maybe even a promotion for you pioneering efforts? Here's an exprimental example I've running at the moment for a massive open online course (MOOC): http://bbpress.matbury.com
I hope this helps! :)