I'll cut Fergie a little slack, because the only reason she was the one singing Sweet Child O Mine in the first place was Axl's mic died. There were multiple technical problems during that show, making it even worse than it was scheduled to be.

Christina Aguillara is a different story. IMHO the only reason she messed up the words in the first place is she was concentrating more on making it "Christina Aguillara sings Our National Anthem," and jazzing it up into something that it's not, than on going out and singing it in a way that shows some respect. IT'S NOT A JAZZ PIECE!!! It annoys me no end when I see someone go in front of a crowd and try and improvise on "The Star-Spangled Banner." When you go out there and sing it, it's not about YOU, it's about what it stands for. Even if she'd gotten the words right, it still would have been a pretty bad rendition, IMO.