As I'm sure many of you already know, cell phones (mobiles) are everywhere here in Africa. On the Kiva Fellows blog, one of the Fellows in Tanzania pointed out that "cell phone service is better than in the U.S., but you can't get running water," which is about right.
In a place where electricity is sketchy or unavailable and people are very itinerant, cell phones are fantastic. And in a place where mail service is pretty much non-existent, it's all on a pay-as-you-go system. On every street practically every shop allows you to buy airtime minutes: 2,000/= for a small slip of paper with a scratch-off part that reveals a code you can enter to add more minutes. Receiving calls is free, though, so even if you are out of minutes, you can still get calls.
People don't answer phones here; they pick them. "He's not picking," is a refrain I have heard often, and may suggest that the receiver doesn't want to talk to you (as when you are trying to visit a borrower who is late paying back a loan).
I bought a cell phone soon after my arrival here, and it has been an amazing tool. Even relative strangers give out cell phone numbers freely, and entering that information into my contact directory has been the best way to keep track of who is who.