This actually stemmed from an idea Nathan Eagle had a few years ago trying to Mechanical Turk the developing world. The idea being to send micro-tasks (often translation) to people via SMS, then paying them upon successful completion.

That never took off with much traction that I know of, primarily because it was hard to find micro-tasks that were worth the money.

There is this very weird legal distinction in Africa between airtime and actual money. Mobile money systems like mPesa are more and more prevalent, but if you stop and think for a minute everybody has been loading their phones with 'cash' for time eternal. (and been able to transfer it about)

It is only the addition of being able to remove the money from the network as cash that makes mobile money different. But as pointed in the FA, people spend so much money on airtime that for small values of x mobile money and airtime are equivalent.

In any case, smart move by Nathan, it is much easier making deals with carriers to buy large swaths of their airtime than integrate with their totally varied mobile money systems.