Digitimes claims that the notebook industry is increasingly adopting Magnesium alloy chassis. In 2003, orders are expected to double.
They mention Apple as one of the companies increasing their orders for Magnesium alloy. Apple currently uses a Magnesium frame in their iBook laptop.
Of interest, the original NeXT cube was built out of cast magnesium... which the editor of NeXTWorld magazine finally got a chance to set ablaze in 1992. (An interesting read.)