K.M. Richards
Program Director, The Eighties Channel™
As obsolete as it may be technically in the 21st century, it's not going to kill anybody broadcasting on the terrestrial airwaves to put call letters/COL at the top of the hour. There are internet broadcasters that would LOVE to become actual radio stations and proudly say call letters/COLs.
I do not favor keeping an antiquated requirement in force, even if it doesn't "kill anybody". The audience doesn't care anyway, PPM doesn't need it, and in diary markets (or so Nielsen tells me) the vast majority of listening entries are by frequency, and most of the rest are by program name/air personality.
KRKE got credit several books back for a diary entry of "Casey Kasem" during the timeslot where we air his classic American Top 40 shows. And this is a station that uses its call letters all during the hour!