The "rumor" forum is a good place for this link.
Notice that all of the facts are predicated on phrases like "...are thought to be" and "...are reported to have" and the ever popular "...is said to be." Even the links quote unnamed sources who quote other unnamed sources who also include the uninformative quotes of "...rumors have surfaced that..." and so forth. I have followed almost every link and not a single hard data point has surfaced.
Given the crap that the PC industry uses to try to compete with Apple, I have no doubt that the Mac line will continue to eat the competition's lunch, but I doubt that it is because of a lack of aluminum alloy or lathes. Right now, just in a single industrial area of Texas there are rows and rows of idle CNC lathes that the owners would love to lease out to make bathtubs for laptops, and this isn't even a depressed area. And across the unemployed country (heck - the world) there has to be hundreds or thousands of similar machines waiting for work.
And the idea that only Apple somehow can figure out how to machine a shape out of a flat piece of aluminum is ridiculous. Apple engineers have lots of smarts, but they don't have a monopoly on smart engineering.
I think the real answer is that Apple "got thar fustes with the mostest." (Apologies to non-US residents, or US residents who went to a public school in the last 30 years. The quote is from a Civil War general, Bedford Forrest.)
