Drawing on course registration data, Mixable invites students in virtual rooms with classmates in each of their courses. Once there, it lets them post and start comment threads about links, files, and other materials that might be relevant to the course — or not. The point is, there is no administrative authority determining what should (or must) be posted or discussed, and students are free to abstain from participating — just like on Facebook. Professors can join in, but they don’t run the show. And students can choose to make posts viewable by some classmates and not others. “In essence, the conversation is owned by the student,” says Kyle Bowen, the director of informatics at Purdue.