I understand why, for example, my little sister likes him: she's 11. That's the age group he's aimed at, or at least the age group he SHOULD be aimed at. Anyone over that preteen age shouldn't like Justin Bieber's music. It's catchy, sure, but that doesn't make it good. That means, it sticks in your head and you remember the song, whether you hate it or not. That's what the market people want. Lady Gaga uses the same logic. Repeat "Ra ra ra ra ra ra ra ra ra romance" or "Pa pa pa pa pa pa poker face pa pa pa pa poker face" and you remember the song, hate it or not.