Here is one simple suggestion: a restaurant payment model. If a learner can pick whatever learning materials they like from a menu and only pay for the material they consume, then the incentives align: 1) the learner wants to finish to gain nourishment (knowledge and credit), 2) the provider wants to offer a dining experience (content and delivery) that learners will, in fact, finish, enjoy and recommend to friends. When these incentives work, the next day, more people come and consume more. Instagram demonstrates how quickly such an on-line establishment can scale.
Restaurant model incentives become more interesting when they include an invitation to come into the kitchen to help with the process to cover the costs. If a learner can collaboratively develop, edit or share content (to the "end of the row" -- mixing metaphors), they can work off some of their payment obligation. Wikipedia manages this type of reciprocal value creation without requiring that any money change hands (the use, work of maintaining and donations are all voluntary).
A restaurant model also suggests a reduction in "meal size" might be well received. Instead of a big, periodic tuition bill (cafeteria-style dining), learners could be billed, continually, for what they complete, like the list of food and drinks on a restaurant bill. Since completion of learning experiences has market value, that bill would come due when the learner wants to claim completion, either to get a job or as a prerequisite to other learning. Reviewing that billing statement would give a learner a clear picture of their learning progress and their investment in themselves, while serving as a type of e-portfolio. What firm is closest to delivering on this idea?
So far, having started in March 2012, the SlideSpeech system supports public, collaborative content creation and sharing with distribution on the web and mobile devices, but -- the point is well taken -- the project won't be a success until both "someone benefits" and we can "do it sustainably."