MOOCs: The Challenges for Academic Librarians", (Australian Academic & Research Libraries, 1 Aug 2013) provides a useful checklist of issues raised with Massive Open On-line Courses (MOOCs) for academic librarians. As Barnes points out, MOOC have no formal entrance requirements, are free, delivered on-line and have thousands of students. But the issues MOOCs raise are not new and have been addressed by universities offering online courses (and distance education on paper before that) for decades.
Recently I have been working my way through some of the books written about the UK Open University decades ago, which I found while wandering down the shelves at the ADAF library. All the issues brought up by MOOCs, to do with courses with no formal entrance requirements, low cost, students with disability, copyright clearance and having tens of thousands of students are covered there