The always-insightful Robert Paterson left a good questioning response to my last post about privacy and responsibility: "Why would the teacher ask her students to get a blog - they are free at that level - now the school is not on the hook. The teacher then gives good blogging lessons?" This is probably the way to go, but I don't know if it's watertight. Let's say the English teacher gets everyone in the class to sign up for a LiveJournal account as part of a journaling assignment, and someone in the class uses that account to broadcast something nasty (threats, hate, porn, whatever). Even though the service is outside the fence (not hosted internally or installed on school machines) and the student's inflammatory entry was not part of the assignment, could that teacher still be in trouble? You'd hope not, but in these days of blame and liability, people get more concerned with covering their butts than facilitating innovative learning experiences.
Charles was also following the conversation, and pointed out the importance of small groups in getting learning communities going. This makes a lot of sense for assignments with a set number of students -- I'm trying to extend that thinking into a system that could have thousands of students spread all over the continent...maybe you could still form "study groups" based on interests, rather than affiliation with a single class. But I'm also realizing that it would be easy to associate students by school...perhaps those systems could be combined.