Nearly all U.S. adults have cell phones, and 1 in 4 uses a smart phone, compared with about 16 percent last year, Carson said.

Nielsen, which surveyed 4,000 mobile-phone subscribers in August, predicts that the majority of mobile subscribers in the United States will have smart phones by the end of 2011.

via AppNation opens to sound of cha-ching.

Nielsen surveys are sound.

The last survey in June showed 20 percent penetration for smartphones in the US.

asymco | 20% of American subs have a smartphone with 1.2 million switching every month