The demand for books, music, news, TV, phone calls is constrained by the time that people have. In a mature market (e.g., the US) that time is growing at best at the rate of population growth (low single digits), but in reality is likely to be shrinking as other online activities (e.g., social networking) take up time. The supply for all of the above, however, is increasing by one or more orders of magnitude, as anyone can be a publisher and as the cost of bandwidth has plummeted. The basic m...