Leighton Meester's body is smokin', but by no means curvalicious. So why am I using her as a poster child for curves? Because in her BCBG dress, she proves that you don't need major curves to look womanly. Here, her body looks more hourglass-like than usual, thanks to the dramatic racerback bodice of her LBD.
Notice how the straps sit closer in, away from her shoulders, and how the sides dramatically curve below her armpits? That inverted cutout draws in your gaze and makes you picture an hourglass figure. Of course, a body-conscious fit also helps to move this illusion along. Watch out, dangerous curves ahead!