A year and a half in the life of Miley Cyrus

This was Miley Cyrus, about a year and a half ago:

And this is Miley Cyrus now (caution: NSFW, and really boring, just showing it to make a point):

One question: What the heck happened? Whether or not one likes her style, the first video shows that she is a decently talented young woman. The second video shows that she is a brain-damaged slut puppy.

Is Miley sui generis, or is she the perfect metaphor for American youth?