Whose Side Are You On? Christina Aguilera vs. ...

From The Wanted to Kelly Osbourne, see who's hit a sour note with the singer

JUSTIN BIEBER

Kissed, then dissed? When the Biebs appeared on The Voice, Aguilera seemed to scowl at the teen star after he stopped by her chair for a quick hello. Though their brief interaction went viral, the judge defended herself on Twitter, writing, "The media loves spinning stories... Can't a girl have a little #BieberFever after getting kissed by the Biebs?"