A pedestrian walks past a Vodacom-branded billboard at a taxi rank near Vodaworld, the headquarters of Vodacom Group Ltd., Vodafone&#39;s biggest African business, in Johannesburg, South Africa, on Monday, January 28, 2013. Almost two decades after Vodafone Group Plc entered Africa, the region -- where most people earn less than $2 a day and mobile phone towers run on diesel -- is turning into one of the company&#39;s biggest profit generators. Photographer: Nadine Hutton/Bloomberg via Getty Images