If you want an expert estimate of the sophistication of the talk radio audience, one way to get it, as Scoobie Davis
pointed out, is to listen to the ads they run. I tuned in Limbaugh for a few minutes this morning; one of the ads his guest host was running was somebody who was selling an explanation of how you could not only stop paying taxes, but could also get the IRS to refund any past taxes you may have paid while under the misimpression that taxes were mandatory rather than optional. One of the major sponsors of their morning program, whose ads ran seemingly several times a morning every day for years, was a law firm which specialized in assisting people who were being sued by the IRS for nonpayment of past taxes.
  posted by Alex at 12:56 PM