Are Mashups the End of Music Genres As We Know Them?

Some of the best things to be found on the internet are music mashups! It's a strangely pleasing experience to listen to totally unrelated artists commingling on the same music track. Mashups are awesome because they break genre expectations, which makes us think: why have genres at all? Nowadays there's so much cross-pollination in music and art, creating more and more sub-genres, that the larger genre categories are becoming a useless relic.