The New York Times has an AP story:
Cell phones made up 74.6 percent of all African phone subscriptions last year, says the U.N.’s International Telecommunication Union. Cell phone subscriptions jumped 67 percent south of the Sahara in 2004, compared with 10 percent in cell-phone-saturated Western Europe, according to Mo Ibrahim, the Sudanese who chairs Celtel, a leading African provider.
An industry that barely existed 10 years ago is now worth $25 billion, he says. 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.