LOS ANGELES (Reuters) - Britney Spears hasn't even taken her seat as the new judge of "The X Factor," but the pop icon is already getting a lesson in the media glare of live, talent show television. Spears had barely wrapped up an appearance in New York confirming she is joining the singing contest before the celebrity knives were out, raising the question of how well the singer, who went through a public meltdown in 2007, can handle all the newfound attention. ...