Several years ago an especially inept burglar plied his trade in Loudoun County, Va. While he was at work one night in an empty house, he was seized by a universal concern. He wondered what the future held for him. So he picked up a telephone, called a psychic on a 900-number -- and used his real name in making an appointment.
The Washington Post reported: "When the homeowner found the charge on his telephone bill and alerted the sheriff, the psychic gave up the suspect's name, dropping a dime on him even though he'd had a $250 reading."
The lady had dropped a dime on him. The Random House Dictionary of American Slang dates the usage from 1966. To drop a dime is "to inform on someone by making a telephone call to police; to inform or betray; to fink, tell, crack on, squeal."
Soon, I suppose, she'll have to drop a dollar on him... or somesuch.