The extremely low pass rate for free online courses provides some evidence for this.
This is what's known as a "rationalization". Pick the one explanation you like, and then find some evidence to support it.
To really choose the best answer without experimentation, you write down *all* the possible explanations, and then pick the one that seems most likely.
(If you can do experiments you can eliminate explanations directly - but when you can't do this, the best course is to list all explanations and pick the simplest one.)
A simpler explanation of the low pass rate is that the online courses are of poor quality.
And indeed, many of the online courses are very low quality - especially the ones from high-end players.
The "Probabalistic Graphical Models" course by Stanford is known as a weeder (students get caught off guard with the difficulty), and the online version demonstrates this: the video shows Daphne Koller standing at a lectern droning on and on(*) with no vocal variety, reading the text of the online slides to the viewer... completely uninteresting and making a simple course boring as hell. (sample video.)
I thumbed through the edX course listing and hit on a course I liked - and the introductory video contained absolutely *no* information about the course! The full text of the course description read something like: "Join me as we explore the boundaries of $subject". (Is it a difficult course? Is it introductory or advanced? What level of math is required? What's the syllabus?)
I mentioned it to the head of edX in a private E-mail, and he responded by saying "that's an affiliate course [ie - from an affiliate institution] and we don't have control of the quality or content".
(WTF? You're running a startup and you don't have control over the quality? And he seemed to intimate that he was more interested in building the scope of their selection than the quality.)
Kahn academy is trying to get feedback from students to improve their presentation and make their lectures more effective, but I don't see any other players doing this.
Everyone's just taping their lectures and putting them online(**). The situation won't change until everyone burns through all the seed money and has to start making a profit based on results. For example, edX got $60 million in seed money, and they're burning through it with no viable business plan.
(*) Keep in mind that I'm critiquing the course, and not Professor Koller.
(**) For a counterpoint example, consider Donald Sadoway's Introduction to Solid State Chemistry, which is *not* a MOOC lecture series but is free for online viewing. Light years ahead of any MOOC course and well worth viewing.