Intellectual Property vs. poetic convention

YouTube songs that mix languages are sometimes (often?) removed "due to terms of use violation," which usually means copyright infringement (unless we are talking of obscenity, which occasionally makes it to YouTube). Music might be a different case, but in the case of poets taking lines deliberately from earlier poets, the issue of copyright (or Intellectual Property) violation has to be seen in the context of the poetic convention of allusion, or using a piece of some other poem to refer to that entire poem. It would be ridiculous to have footnotes in a poem (although T. S. Eliot did it famously in "The Waste Land," though still ridiculously). The reader of a poem is presumed to know the history of poetry, to have read the original poems which are being alluded or referred to, to realize that what is going on is not stealing somebody else's words or images but integrating poetic tradition into an existing work (exactly as Eliot theorized in "Tradition and the Individual Talent"). If we take lyrics for a song as an extension of poetry, then we could make a case for lyricists and singers that use lines from earlier artists without explicitly mentioning that these lines are allusive rather than original. I am upset that the song "Liubi, Liubi, I Love You" (described as "Romania's entry in Eurovision 2007, ... basically a love ode performed in six languages") was removed by YouTube.