See "Parks Associates reports almost 50% of U.S. mobile phone users pay for Internet; global data revenues to reach $500 billion by 2015" - here and here.
Compare to "Infonetics: Mobile Broadband Service Revenues to Triple by 2014" - here, forecasting $870B in 2014.
“Data services are a future revenue driver for mobile operators, but mobile broadband creates a new set of challenges for them .. Consumer desire for richer mobile experiences and the market demand for services and applications built on open access could undermine their walled-garden business model. Operators will have to adapt their business models to sell more value-added data applications on top of access services. The key question is what types of mobile data applications will have a broad appeal and help operators differentiate from many would-be mobile service offerings from third-party aggregators and distributors.”