(AM) Radio is a fad, it won't last.
TV is going to kill radio
FM radio is going to kill AM radio
The internet is going to kill radio.
For 90 years people have said that AM is on it's death bed and yet it's still here, and as David pointed out, only a few AM's have handed in their licenses, and those were either stations that shouldn't have been licensed in the first place, or had very bad facilities.
It is still here, and will be for a while. When over 90% of people in the United States and Canada still listen to radio on a weekly basis, and that number is the same now as it was 14 years ago, it brings a Mark Twain quote to mind.
There have been some FMs that have also gone silent. We had one in Ottawa that went silent in October. It's not likely to come back, and maybe a signal challenged FM will move to that frequency. None of our AM's will be flipped.