Here is a more recent study (than the one I mentioned on Saturday) by Pew on who is using the internet and how they are accessing it.
I have not read the entire report yet, but the point I was trying to make was that there are many people who use their mobile devices as the primary means of accessing the internet. From the overview:
The rise of mobile is changing the story. Groups that have traditionally been on the other side of the digital divide in basic internet access are using wireless connections to go online. Among smartphone owners, young adults, minorities, those with no college experience, and those with lower household income levels are more likely than other groups to say that their phone is their main source of internet access.