If you end up contracting one of the more vicious strains of breast cancer, you'll have to get the mastectomy and the cancer still has a good chance of killing you.

Young girls have gotten preventative mastectomies after seeing how horribly their mothers and aunts have suffered. They figure that they're probably going to lose their breasts anyway, so they might as well do it in a way that's controlled and that leaves room for properly inserted implants.