A report by Deborah Fallows published by the Pew Internet & American Life Project documents an increasing use of the internet for "hanging out online." Those with broadband access and with more internet experience tend to go online "on any given day for no particular reason, just for fun or to pass the time." 30% of internet users overall responded that they do this.
The report also documents that the younger the user, the more likely he/she is to use the internet this way. The report also states that 52% of Internet users send or receive email on a given day, 38% use a search engine, and 31% get news online.
What would be interesting to find out would be how many people use their computers for internet access only on any particular day. (Of course, I'm thinking about an Internet "appliance.")
The report can be found at http://www.pewinternet.org/PPF/r/175/report_display.asp.