Fred Wilson mentions on his blog that plenty of people are telling him that radio is dead. He has some interesting data from JD Power on what consumers think about satellite and HD radio in their cars.
My own view? Satellite threatens FM much more than AM. Those who still listen to AM often do so for local reasons – news, traffic, weather, sports, etc. FM has far less of a local connection, since much of it is generated by big radio conglomerates anyway.