Pew has just released some new survey data (n=3,000) -- a kind of gadget census -- that shows 85% of Americans own cell phones (vs. PCs (59%) or laptops (52%)). Three-fourths of teens have mobile phones and a whopping 96% of 18-29 year olds own mobile phones.
The total US population today is 310,480,361 people according to the US Census Bureau. There are about 225 million adults over age 19 in the US (based on 2008 data). If 85% of them (which doesn't include teens) own mobile phones that means 191,250,000 adults in the US today, using the Pew data.
According to comScore there are 212.6 million PC Internet users (August, 2010). When cell-phone owning teens are included (30.2 million) there are 221.5 million mobile phone owners in the US. Mobile Internet penetration varies based on handset type (feature phone, smartphone, iPhone). But the aggregate Nielsen mobile Internet number is now 80 million people in the US.
Globally JP Morgan and others have predicted mobile Internet penetration and access will be greater than PC Internet access by 2014. In North America we may see the crossover happen a couple of years later -- but it will happen.
Here's the demographic breakdown of mobile phone ownership, according to the Pew study:
The Pew data also discuss tablets and eReaders as a growing category. According to Pew, "Around one in ten Americans with annual household incomes of $75,000 or more own a tablet PC or e-book reader, while fewer than 5% of households earning less than $50,000 per year contain one of these devices."