I love reading about how various cultures (e.g., local, youth, etc.) re-appropriate common practices and transform them into something that is essentially different. In this Reuters article about cell phone usage in Africa, missed calls are being transformed into something useful:

You beep someone when you call them up on their mobile phone — setting its display screen briefly flashing — then hang up half a second later, before they have had a chance to answer. Your friend — you hope — sees your name and number on their list of ‘Missed Calls’ and calls you back at his or her expense.

It is a tactic born out of ingenuity and necessity, say analysts who have tracked an explosion in miskin calls by cash-strapped cellphone users from Cape Town to Cairo.

As an FYI, this missed call phenomenon also happens in the UK, at least in the context of (pirate) radios and DJ sessions where calling and hanging up represents a request to reload (start the song over). I forget what they call it.