In 1986, Dan Rather was assaulted on a Manhattan street, knocked to the ground and repeatedly kicked while his assailant demanded to know "What's the frequency, Kenneth?" Pretty bizarre crap.

This gave us, among other things, the R.E.M. hit of the same name.

Now, though, the mystery is solved, and the culprit has been identified! You'll be shocked to learn that it was a mental defective who thought the media were beaming signals into his head.
Rather Knows The Frequency