Pew just released one of their internet usage studies, which I find helpful in nailing down figures on trends. This study is “Mobile Access to Data and Information.”
“People’s growing reliance on their cell phones, together with wireless internet access from laptops, suggests a shift in expectations about cyberspace. For many people, access to digital information and resources is an ‘always present’ utility for answering questions and documenting what is going on around them through photos or video recording.”
John B. Horrigan, Associate Director of the Pew Internet Project and author of the report
According to the study (December 2007 survey data), 62% of adult Americans have either accessed the internet with a wireless connection away from home or work or used a non-voice data application using their cell phone or PDA.
Author of the report has commentary here.