For me the really powerful thing about MOOCs is that they are an antidote to anti-learning. The completely voluntary nature of them (always on the learner side and often also on the tutor side) means that there is a strong motivation for learning to happen.
They are the complete opposite of environments where people's attempts to force learning to happen prevent it from happening. I am thinking of a college where I was once an associate tutor and there were rules about student dress code and class times - even if a group worked really hard and learned loads they couldn't finish a course before a certain time. And the grammar school I attended was a classic example too.
I have come across low motivations in other formal environments even where all the learners were there voluntarily but the informal nature of MOOCs makes motivation their primary mechanism and reason for existing. I am not sure why people worry about high dropout rates - it may be a bit deflating for someone to set a course up and then loose lots of learners but that must surely go with the territory?
Thinking about whether MOOCs are suitable in my own context - there is a school of thought that commercial providers will do them as a way of promoting their wares - many already do free seminars, webinars etc for this purpose. If they are really good quality then word could get around about the quality of the provider but I know many people in the corporate world are concerned about taking a "free" service and then being aggressively sold to.
Where I think they have a major role to play is in the professional development world. I am very actively involved with some professional bodies and I think MOOCs could be a valuable service to support continuing professional development. Looking at how these bodies work though I can see the model shifting a bit and almost becoming MOOCs in reverse.
Whereas a MOOC may contain a core of learners who are paying to be part of a formal course and a wider group of informal learners, I can see professional bodies making open courses available free to their members and charging fees to non-members as a way of demonstrating the benefits of membership.
Not sure this matters - MOOCs have a big role to play here - am off to see if I can find any professional bodies that are already doing this....