Regarding the earlier question (posed a day or two ago) about why there is no sale of broadcast spectrum given that only 15 percent of Americans receive their TV via over-the-air signals:
To begin, the major networks have something like 40 percent of the U.S. viewing market (I'm not sure of the exact percentage), which means they have a little less than half their viewers accessing them via over-the-air signals and half accessing via cable, satellite, etc. Thus, if over-the-air signals disappeared, the major networks would lose a huge number of viewers and perhaps not have a viable business model. Note that those who then subscribed to cable or satellite would have more options and thus might not be so inclined to watch the major networks. A related point is that the Natl Assoc of Broadcasters (NAB) is extremely powerful. Broadcasters offer an efficient way for Congress members to advertise, which may be related to why we have a campaign financing issue. Tom Hazlett made a good case (see "Abolish Television" piece in Financial Times, or "The Spectrum Craze..." in Harvard Journal of Law and Tech) that we could auction off the broadcast spectrum, use the proceeds to buy cable or satellite for everyone who still uses rabbit ears, and have enough left over to develop a cure for cancer, an AIDS vaccine, and an over-the-counter pill for multiple orgasms. (Okay, he didn't exactly say all of this, but it is valuable spectrum.)
