Gangnam style marked a new milestone over the weekend as it became the most-watched item ever posted to YouTube with more than 800 million views. It has even edged out  Justin Bieber  – such is its success. But Korean rapper Psy's Gangnam style is only the latest incarnation of a pop sensation that fuses video, youth, dance, and social media into a virtual club scene that never goes dark. Euny Hong  is the lifestyle editor for Quartz.