Well, since this said celebrities, and not just musical acts, I will say the Kardashians. The only good thing I can think to say for the family is that they're very smart business people. It takes a lot of skill to be so famous for having so little to offer.
Other than that...I can see why someone would stan for say...a YouTuber or a Viner. I see literally no difference between being famous because a big corporation decided to do massive promotional campaigns for them, or because someone decided to put themselves up for the world to see, a garnered an audience through the power of the internet. At the end of the day, these people are known by many all around the world, have fans, etc...only difference is the mediums at which they are presented.
Taylor Swift (nowadays)
Justin Bieber of course
Ariana Grande
Avril Lavigne (Sad I was aa fan of her till Goodbye Lullaby came out, but her music turn into an embarrassing mess)
and maybe Britney Spears (she's a great person I absolutely love her and her carerr was so promissing, but nowadays... Sad).