Rebecca Black uses too many vocal adjustments in the recording of her official videos, but a private recording shows sound, look at her official "Friday" video to see what I mean.
Yes, Amy Winehouse is dead, but while she was alive she was too much of a druggy & drunk to effectively handle a decent performance, especially in the last couple years.
Lady Gaga, sure she's got her strengths, but her outfits tend to be restrictive on her breathing and sometimes she loses sound.
Glee - New Directions, I love the show, they're a "work in progress" and they finally got their act together in New York, other than that damn kiss, less relationships more technical.
Glee - Vocal Adrenaline, yes they're good, but I find sometimes they have been pushed so hard they're worn out by the time competitions come around. They need to work on their breathing techniques so they're not so worn out.