Justin Bieber's biggest fan is his mentor Usher.    Gotta hand it to the two of them - together, they have taken over.   Wonder how much $ Usher gets from the business end of Biebs?    From an MTV interview:

Asked what he admires most about Justin, Usher said, "His excitement and innocence in it. And I don't mean that in a light way because I think that he's absolutely enjoying every moment of it, as any young man his age would, but in a different way because [of] the hard work that has gone in and led to the dream that has become a reality. And every time you have an opportunity do something incredible, I tell him to do his best and be conscious that what you're doing today should last forever and eternity."

(via Usher Most Admires Justin Bieber's 'Excitement And Innocence' - Music, Celebrity, Artist News | MTV.)