Correct me if I'm wrong, but Duke's program is not full-online degree. I know that they have established 5 campuses throughout the World and that one has to sit for an exam in one of them. So, it's more like an executive MBA with 5 different locations and with online lectures.
On the other hand, I don't know what to think of fully online degeers. I mean, if you don't have to come to the university ever and if you can take your exams online, that sounds pretty much like a diploma mill to me. You don't have even to bother with your exam, you can hire somebody to do it instead of you. That way, any individual in this planet whose parents have enough funds could becomme a member of your alumni. That is definitely not something that is appealing to me, and, what is even worse, I'm affraid is not going to be appealing for potential employers at all.