It will also wreck the generators and any synchrnous motors turned on at the time. This story has more of an Onion flavor to it.
Drifts in frequency across what is supposed to be a unified grid will also randomly pop circuit breakers and make emergency power routing (say in the event of storm damage) more difficult or impossible.
This is gonna affect my Acoustics Research turntable, with its synchronous motor. Gonna hear a little more flutter, I suspect.