For some time, the debate in the survey research community about how to respond to the increasing nonrepresentativeness of phone line-based surveys has been raging, but based on data I read in the Economist which puts more than twenty percent of households in the United States as being "mobile only," I think this debate can only be getting ready to escalate.  The article has a much fuller presentation of the issues than I can offer, but it does raise in my mind the difficulty of pursuing any household surveys in the future which rely solely on random digit dialing.  In the past, efforts like the Panel Study on Entrepreneurial Dynamics, have used such techniques to arrive at a representative sample of the U.S. population.  For efforts which are aimed at a business population, I suspect there is less of an issue as it is my suspicion that most businesses larger than a couple of employees still maintain some form of land line phone, although I don't believe we have data on that.