A number of individuals expressed concern with the figures cited in the New York Times article. The rebuttal criticized the methodology of Quarterman's Internet Demographic Survey. Here is an email response from John Quarterman to a draft of Hoffman and Novak's Hotwired article. Select one of these two topics. This is very important, since there are multiple definitions of an Internet user, and a single definition may not be sufficient.
Usage can be within the United States, or worldwide.
You might separately estimate the number of users of the Internet and the number of potential users. You may wish to include users of non-Internet services such as Prodigy and America On Line. Explictly support your estimates with clearly cited secondary data sources. You may well have a range of estimates, each based upon different assumptions. You can and should be creative in terms of how you estimate these numbers.