The bottom line is more do, than don't. AND its often done without the singers knowledge. Its not up to them, its up to the producer/label. And things like Melodyne and Autotune work way better when used less- slap them on a good tuned vocal and it becomes even better pitchwise. I love it when people think they can tell... No, you can ONLY tell when its working too hard. And then people say, "I don't like how it sounds"... Right. If you autotune a track and send it back out to the board at mixdown, it will fix 90% of the change you heard- just by returning analog. The singer is usually long gone by the time pitch correction is applied anyway. And when used properly on a decent original take - sound stellar. Now who thinks an artist is going to admit pitch correction....