Miley explained in an interview with MTV just where she got her inspiration for the dance moves that go with the song Party in the USA. 

Miley wanted the dance to be a lot like the movie Grease, which was her parent's favorite movie. She wanted to pay homage to them with the dance as well as paying homage to Grease and its era.

However, there is no problem with having Grease be the inspriation behind the dance, the issue is the dance itself and Miley's moves. Some people think her dance is just too sexy, and that the dancers dance too closely .