Well, edX is not particularly novel, given all the other free online courses there are.
On top of that, cheating is rampant
, which I find puzzling. These are courses with no credit. The only benefit you get is what you learn. And people still don't want to learn, they want to cheat their way through.
Apart from accreditation, the lack of direct interaction with instructors is probably the biggest thing that sets this this sort of system back. Sure, you could have one professor teaching 10,000 students... which means the prof never has time to directly interact with more than a tiny handful of those. If you think things are bad in auditorium-sized college classes now, I can only imagine how much worse the situation is when the class size goes up an order of magnitude (or two.)
It's good that knowledge is becoming cheaper and more accessible, however this is not something we can simply thank online universities for. It's been a growing trend since the Web first came to prominence. People like sharing information, and many of them tend not to mind doing it for free.
Touting this as the "most important education technology in 200 years" is more than a little hyperbole.