I had a feeling this would be brought up and as I predicted.
IMO not the worst ever look at Ashlee Simpson's lip syncing fiasco. Also if you're going to judge an artist by one bad live performance then shame on you because she has some really good material and good live performanes under her belt. I do agree it was a big opportunity for her to shine though and she didnt. Check out her thread.
I think people just like to hate sometimes because they're afraid of what's new and up and coming. She has received a lot of criticism but you know what? Dont listen to her if you dont like her. Simple really. Leave her alone or at least give her a fair listen I say.