Time Magazine published an interesting article about Auto-Tune and how it has changed the pop music. Industry heavyweights like Rick Rubin as well as Auto-Tune addict T-Pain explain how and why Auto-Tune has become a standard tool in creating good and bad, clean and weird vocals. Check the podcast for audio examples.
Auto-Tune: Why Pop Music Sounds Perfect
Time Auto-Tune podcast (iTunes link with audio examples)