I love the iPad's aluminum back. It makes it feel solid, which is a must for its thinness. But it's heavy too. Apple may be thinking about the possibility of making their iOS tablet lighter by changing it to carbon fiber.
At least, that's what their latest iPad patent is all about. Carbon fiber is light, but it's also brittle and it can crack if it's bent or rolled in the wrong way. Their patent describes a method to create a "reinforced device housing" that may avoid the problems associated with this kind of cases.
However, the patent was filed on May 18, 2009, which predates Apple's purchase of all rights to LiquidMetal technology, a hybrid material with the strength and anti-corrosive nature of metals like titanium and stainless steel, with the benefits of plastics and composites, such as extreme flexibility and easy casting.