Massive Open Online Courses : are they good for education?

Give some history and background about massive open online courses (MOOCs). How do they work? What are their aims ? Who enrolls in the courses? Then ,evaluate them. What is the completion rate? What benefits and problems have occurred? Have they fulfilled their promise? If not, is it likely just a matter of time until they do so, or are there inherent weaknesses in the very idea of MOOCs? ESSAY SHOULD BE APPROX 2000 words