Logic suggests that there is some positive relationship between broadband availability and economic growth, though it is hard to separate "causal" from "correlated" effects.
"We estimate that between 1998 and 2002, communities in which mass-market broadband was available by December 1999 experienced more rapid growth in employment, the number of businesses overall, and businesses in IT-intensive sectors," say researchers By William H. Lehr, Carlos A. Osorio and Sharon E. Gillett of the Massachusetts Institute of Technology and Marvin A. Sirbu, of Carnegie Mellon University. See
http://www.broadbandproperties.com/2005issues/dec05issues/Measuring%20Broadband%20Eco%20Impact,%20Lehr,%20Gilett,%20Sirbu.pdf.
Connected Nation likewise argues that broadband promotes economic growth. See
http://connectednation.org/_documents/Connected_Nation_EIS_Study_Full_Report_02212008.pdf. The Organization for Economic Cooperation and Development likewise concurs. See
http://www.oecd.org/dataoecd/62/7/40781696.pdf.
What remains unclear is what relationship exists between "ultra-high" broadband and merely "fast" broadband. One might legitimately point out that it is hard, in advance, to determine the impact of features not widely used. But the question is a fair one, given the huge investments that will have to be made to provide 100 Mbps service, for example. If one assumes investmetn capital will be scarce, a rather reasonable assumption, then the question becomes a matter of where to make broadband investments to reap the highest social reward.
These days, it is hard to argue that returns are not greater in the wireless, than in the fixed network sphere.
Nor is the eivdence about how broadband availability affects rural areas uniformly clear or positive. See
http://bits.blogs.nytimes.com/2009/02/20/rural-broadband-no-job-creation-machine/. In fact, Professor Raul Katz says it simply isn't clear whether broadband in rural areas is all positives, and no negatives. See
http://www.elinoam.com/raulkatz/Dr_Raul_Katz_-_BB_Stimulus_Working_Paper.pdf.
Beyond that, the issue is whether the economy and society are better served by investment in mobile or fixed networks, beyond a certain point, if choices have to be made. And few would doubt that choices in fact must be made. There simply isn't enough capital, or enough demand, to invest very aggressively in both fixed and mobile networks, if the goal is 100 Mbps on the fixed network and 50 Mbps or more on the wireless networks.
That's one reason why fixed network investment has been "starved" so the wireless network can be fed, or why the number of employees in the wireline segment have been shrinking, while the number of employees working on the wireless network has been growing.
The issue is not so much whether there will be investment in either network. The issue is how much investment, and where those making the investment believe they can earn the higher returns.
The point is simply that, so far, there is no real evidence that the return from 100-Mbps networks is twice that of 50-Mbps networks, in terms of economic growth or social welfare.
Just about anybody likely would argue that a 100-Mbps network is better than a 50-Mbps network. The rub is that it is harder to determine whether 50-Mbps wireless networks might be even better, or whether 50-Mbps fixed or wireless networks would provide more economic growth and welfare than 100-Mbps fixed networks.