Litigation
Apple has threatened legal action against those who made themes similar to their look and feel.
Despite accepting (for the most part) Apple's right to their copyrighted artwork, the skinning community took exception to their heavy-handed actions against all Aqua lookalikes; Stardock's Brad Wardell contrasted the company's litigious approach with Microsoft's approach to incorporating third-party skins into Windows XP.
Read more about this topic: Aqua (user Interface)