If ear piercings are permitted, is there a prohibition against a woman getting a belly-button piercing? Would it not be considered immodest since the whole point of the piercing is to show it off? Is it really necessary for a woman to get a belly-button pierced to appear more beautiful? What about piercing in eye-brows, tongues and other parts of the body that many Orthodox Jews would typically frown upon as "trashy"?
The piercing itself is not the problem; it's the message behind it. If it means to copy the non Jewish way of immodest appearance and licentiousness it's prohibited. If it's purely for aesthetic and beauty purposes, it will not render a problem just like earrings don't. I have a feeling that piercing nowadays in more of the first category.