That stuff is out there: http://btjunkie.org/torrent?do=stat&id=37844420367 eed57ec7300ee938ded2e9e9c599910a7
Bringing in the lawyers will only push the skin's popularity up for a few days/weeks and will cost apple a chunk of good will.

Note: linking is not a crime. Neither is fair use (exercised by bloggers/journalists posting about the iphone and using a screenshot).