This trend has been burgeoning for some time, beginning with the Pussycat Dolls, Fergie and other friends of humanity in the mid-late noughties.
It reaches an apotheosis though in the figure of Ke$ha. A sample lyric from her recent single "Blah Blah Blah" shows a combination of sexual libertarianism and ennui-bordering-on-total-hopelessness for which there can be few precedents in the history of western art:
Boy come on get your rocks off
Come put a little love in my glove box
I wanna dance with no pants on
Meet me in the back with the jack and the jukebox
So cut to the chase kid
'Cause I know you don't care what my middle name is
I wanna be naked
But you're wasted.
I would like to reiterate that what I find objectionable about this is, not the absence of morality and/or humaneness in the depiction of human sexuality, but the total lack of purpose therein. Contrast this with, say, "Sympathy for the Devil".
These lyrics express a dystopia that is now very real.
See also below article on 3OH!3 + Katy Perry.