You have to say fuck more than once to get a parental advisory sticker.
Just like you have to say it more than once to get an R rating on a movie.
What cracks me up is this: my radio station plays "This Love" and doesn't not edit out the part about her coming every night, which I don't think they should. If you get it you get it, no need to bleep out a word kids don't know has a sexual connotation. BUT in Matt Nathanson's cover of "Laid", they completely removed the line "She only comes when she's on top". The use of "come" is the same, obviously, but they only cut it out of the one song. Hmmm...