Verizon has found the fountain of youth. The largest U.S. telecom company by subscribers reported on Tuesday that wireless revenue grew 8 per cent in 2012. How do sales grow at three times’ gross domestic product, and margins expand, in an industry that (given cellphone penetration) should behave like a utility? The answer is the smartphone. In 2012, Verizon added 5 million contract customers. The number of its customers who use smartphones, and therefore pay up for data services, rose by 15 million.