LOS ANGELES (Reuters) - Time was when TV talent shows set out to turn wannabes into stars. These days? Not so much. It's the celebrity judges who are raking in the cash and using TV contests not only as a way to re-launch a fading career, but to further boost a thriving one. For music stars in an era of weak record sales, the trend spells victory for their bank account, but for fans and the music industry always hungering for a new star, it's a loss. And for TV networks, the once cheap-to-produce shows are ever more expensive, yet they don't always pay off in bigger audiences. ...