Nielsen’s State of the Media: The Mobile Media Report provides a snapshot of the current mobile media landscape and audiences in the U.S. and highlights the potential power of mobile commerce in the near future.
Key findings:

This report draws from a broad range of Nielsen data sources, including: Nielsen’s in-depth monthly surveys of mobile consumers (more than 300,000 consumers surveyed each year); Device metering data from the iOS and Android smartphones of thousands of consumers who have volunteered to be a part of our research panel; detailed, monthly analysis of the cellphone bills for 65,000 lines in the U.S., again, thanks to volunteer panelists.
For more, download State of the Media: The Mobile Media Report Q3 2011.