I have to wonder is some of you ever even follow other musicians or bands remotely closely outside of U2? Some of you act like you've never seen this type of thing. Maybe because I play and see live music all the time I'm aware, but you are all music lovers I would think you see a lot of live music, no? A thousand things can distract you during a show, a new stage, crew trying to tell you something, a fan is screaming something at you, a technical difficulty, whatever you name it and you have to tune it out pay attention to the band, sing, and try and entertain the audience all at the same time... and if you're a little ADD like I am, that's no easy task. I flub lyrics all the time, Vedder flubs lyrics all the time(why do you think he "mumbles" so much? So he can cover it up), I just saw a good friend of mine over the weekend who's been touring one album over a year flub a song she's probably played over 200 times this year, she messed up the intro and jokingly said "you'd think I would know this one by now I'm asked to play it every damn place I go."
It's not a mechanical act.
NBA players still miss free throws.