Too much needed - modern Pop and Country music.

Purposefully too much - like Cher, T-Pain, and Lil Wayne.

There are three levels of autotune, as far as I see it:

In order to push the effect into overdrive you have to purposefully have a bad performance to a certain degree, which is why it works so naturally well for rap artists in terms of singing to the correct pitch. The main contributing factor to an 'invisible' autotune is a great vocal performance. Let me tell you, they all are, but their mixing engineers are doing such a fantastic job with it you wouldn't know. Then you consider all of the artists you think aren't using it.

It's my opinion that the 2010 decade will be considered a 'dark age' of music, partially due to this effect that many artists will come to regret in the future. Take artists like Cher or T-Pain, or even Lil Wayne when rapping, who nearly sound like robots during their songs. More artists than you'd realize use this tool undetectably, while others make it very obvious.

Autotune is the perfect example of a signal processing method that can be used in overdrive as an effect or used properly in a transparent way to improve a performance.

Gsnap autotune presets