I'd be interested in seeing completion rates if people had to pay (put some skin in the game).
I'd like to see the completion rate for people who get actual college credit for the courses - and still have the courses free.
The reason that moocs are not disruptive is because have not been given the power to be disruptive. They still allow the old institutions to get away with their many current shortcomings without facing true competition.
Colleges and universities dangle the carrot in front of everyone's face (like MIT) while not really following through to the conclusion - i.e. granting credit for the work and effort someone invests in learning the material.
In MIT's case, they could offer to have an exam proctored at a local university where someone would walk in the door and be tested. But then nobody would bother to pay exorbitant amounts to show up to the brick and mortar school.
But I submit that the emperor has no clothes. The value of having a college degree (i.e. help in gaining employment) has decreased markedly, as the workplace values cheap workers over qualified ones in the first place. Employers first priority is to make sure that their board of directors and CEOs are well taken care of before anyone else.