Cell Phones in the Third World

This year's Edge question: "What are you optimistic about?" generated more responses than earlier years' questions, so it has been taking me a while to get through the whole thing. The best line I've read so far (I'm on page 13 of 16) is by Sandy Pentland of MIT:

The International Telecommunications Union estimates that in the poorest countries each additional cell phone installed adds $3000 to the GDP, primarily due to the increased efficiency of business processes.