The problem I see with generating cash is the low level of disposable income source within the young demographic that these sites are targeting. The do it your self approach to the borrowing mechanism would be even better if the students could network within a future hiring organisation. For any individual or group wanting to invest in education this could be the next investment bubble. From an investors lens if a student turns out to be the next average paid employee your 6.5 percent or whatever you make on your investment could pay out a solid return. To push the idea even further this social borrowing could foster a revolution of technology.
Big ideas, like that catch phrase "think globally, act locally."