The Air Minute Standard

Economics tidbit of the day, from an article about cell phones in Africa:

Prepaid air minutes are the preferred means of usage and have created their own $2 billion-a-year industry of small-time vendors, the Celtel chief says. Air minutes have even become a form of currency, transactable from phone to phone by text message, he says.

This is particularly useful in Africa, where transferring small amounts of money through banks is costly.