I used this tool to teach the basics of argumentative writing and did it based on the novel, A Long Walk To Water which I then related to real-life events such as immigration, the killing of Cecil the lion and world poverty. The students were able to comment on each other's work which they got a kick out of, and the cool thing for me was, that in case anyone decided to be silly, I got to approve all comments before they went out into the big wide world.
As well as teaching content - so the writing I wanted, I was also able to teach basic computer skills such as how to search for and add photos, the importance of relevant pictures, typing skills and how to navigate around changing font sizes, writing in bold etc. The only complaint I have with the program is that it does not allow you to print the posts. I got around this by taking screen shots of a few pages I wanted, but it would be good if you were able to simply hit 'print' and get the page you want.
It is one of the easiest, most effective and fantastic tools I have used. My students loved it and I highly recommend it.