I have a few ideas about online writing and collaboration. I integrate computers in grades k-2. As any educator knows, what we do in the grades before gets built upon in our students future. How can we expect our students to grow into adults who can collaborate in the workplace if we don't ask them to collaborate at school? Must this collaboration be done online? Certainly not, but the internet provides easy access for it to be accomplished. Other advantages to the internet collaboration via a wiki, google documents, blogs, nings... are that peer editing, and collaboration with students and teachers in other schools and places all over the world can occur. In other words, online writing gives students ownership with a real "audience" to write for. This audience is not just their classmates or immediate family. My youngest students are extremely excited to have their writing placed on a website for others to read. Their enthusiasm to make their writing more polished and thoughtful should be reason enough to use the internet for publishing.
Google documents is a real world application in which we can give our students a real life skill that they can use after their graduation. Students can work together on a single document and not have to be in the same place at the same time. The possibilities for use are unimaginable in the work place environment but are just as applicable in the classroom.
My feeling about online writing and collaboration are, "Why wouldn't you want to use these free tools and give your students the opportunities for learning and pride in their work?"