Bieber Fever, Beliebers... It's just like Gleeks (GLEE) or Glamberts (Adam Lambert Fans)
Girls like him because he's good looking and very talented. Don't get me wrong, I've been on both sides of the argument, but if you pay attention he is a very good artist, and now that his voice dropped he's taken more seriously. A lot of people, mainly guys, say bad things about him because of what songs he sings; nearly all pop love songs for girls... which is another reason the girls love him. They hear him sing all the things they wish guys in real life would say to them.