Conspiracy,tinfoil,espionage,underpants,head,pencils,nose Numbers radio stations - sinister or not?

From Wikipedia: Numbers stations are shortwave radio stations of uncertain origin. They generally broadcast voices reading streams of numbers, words, letters (sometimes using a phonetic alphabet), tunes or morse code. See rickegee's original post for audio samples. More info here: http://en.wikipedia.org/wiki/Number_stations