I don't get it: why do people bother to blank out swearing in songs? The song which brought this thought on was Linkin Park's Bleed It Out, which has two blanked parts, I think. I mean, it's not like you don't know it's there, since there's this conspicuous silence from the singer's track at that point. The fact that it is blanked seems to suggest that the word is only offensive if you hear it, but as long as you don't hear it (but know it's there), it's fine.
Seems very irrational to me. The better way of going that is to dub over it, like some movies do. But of course then the song probably wouldn't make much sense.