It really depends on the problem.i.e, Britney lipsynchs sometimes, cause she dances at the same time.It's only good to lip s. if you have a good reason.i.e., Ashlee is very talented.She can sing, and writes her own music.She lip s. because she has a soar throat, and could barely sing.For all those who say she can't sing, well you're wrong.If you watch The Ashlee Simpson Show, like me, you'll see her sing, without mouthing the words.But there are just some very fake artists such as Hilary Duff, and Lindsay Lohan.Hilary lip s. all of her performances.On Lindsay's latest video, her voice is backed up by a computerish sound, that doesn't sound like hers.If you want to hear her real voice, just watch Mean Girls, during a scene where she sings with the Plastics.When I first saw her video, Rumours, I was shocked.Her voice was backed up, because it wasn't good.I would'nt go to a concert if an artist like Hilary is performing, cause what's the use if your not going to actually hear them sing without a tape.You might as well listen to your cd player.Artists that dance for most of their performances, such as Usher, shouldn't dance too much, cause they get exhausted, and can't sing well.