When someone begins to dislike a band, movie, tv show or any other element of popular culture solely based on the fact that it has become popular.
This is something that hipsters do on a regular bases in order to remain relevant. It is the ultimate betrayal because at one point you consider this band or movie to be amazing and now that it has gain recognition instead of being happy you reject it and call it "mainstream".
Hispter: I used to like Arcade Fire but then they became so main stream. I can't even listen to their music any more.
Non-Hipster: Arcade Fire is exactly the same as they used to be, you just doing the Hipster Betrayal.
Khârn is a favorite champion of Khorne, the Blood God from the Warhammer 40k Universe. He has an insatiable lust for blood and is known as the betrayer for his habit of messily dismembering allies nearby him when he runs out of enemies. In fact, the name Khârn is actually derived from the Arabic word for "betrayer". Despite all this, he is actually a pretty great guy.
I just watched Khârn the Betrayer dropkick a loyalist marine into that cluster of Thousand Sons; he exploded into confetti and viscera. He then gave me a high-five that shattered every bone in my arm. What a guy!