have you ever been to a concert where the performer forgot the words to their own song? Did it bother you?
The first time I saw Ben Folds, he forgot the words to "Zak and Sara" but he made up a funny filler instead of the actual words, so it was good for a laugh and I didn't really care.
The second time I saw Rufus Wainwright, he forgot the words to "Poses," and it bothered me only because that is my second favorite song of his and he forgot my favorite line, "all these poses of classical torture/ruining my mind like a snake in the orchard." It just kind of ruined the dreamy state of the song, but I forgive him anyways because he has a lot of lines to remember and I love him no matter what!