They can't wear bras with them, so a gust of wind, lifting an arm, or leaning over can expose the whole side of their breast, creating what Peter Griffin affectionately refers to as "side boob".
Miley Cyrus' side boob shot was, fortunately for the pap who took the picture, nipple-free. With the way the girl dresses, I'm sure there is a photographer out there somewhere with photos that would be considered child porn; they just could never come forward with them.
But if giving Disney another headache wasn't enough, Miley Cyrus herself has ventured into the place than many pop princess before her have been: the place on celebrity blogs and gossip rags that tell the world that you have gotten breast implants
