There still is a mainstream, it's the old vanguard. Things like the Billboard list artists, TV networks and pop culture celebrities (think Lady Gaga, Katy Perry

There still is a mainstream, it's the old vanguard. Things like the Billboard list artists, TV networks and pop culture celebrities (think Lady Gaga, Katy Perry, Jay Z, Beyonce) are all part of what is considered mainstream. It may not be as culturally dominant as it was in the past but it does still exist.