Machined aluminum block? Don't think so...
I'm exceedingly skeptical about the speculation that it's a new manufacturing process involving what amounts to carving out a machine chassis from a solid piece of metal - if this were even remotely feasible on a financial level, then you can bet that fabrication in much higher volume industries would have adopted it already.
The truth is, if you wanted a form that you couldn't achieve through the standard manfacturing process of stamping/rolling/machining sheet metals, and then assembling with fasteners, the next option is casting, which would allow you to achieve the same or better results than machining out of a solid billet of material. Look at high-end molded monocoque aluminum fabrication for bicycle and vehicle frames, and you'll understand that you can create complex shapes with voids and curves and anything you could possibly imagine - certainly anything you'd need out of a computer casing.
Machining a thin, complex, lightweight object out of a solid billet would be so exceedingly wasteful of energy, labor, and materials, and the required precision so hard to achieve, that it would be too costly to possibly be feasible, even taking into account recycling the waste metal, this doesn't work. I highly doubt that Apple is going to develop it's own aluminum foundry to re-cast new billets from waste, and involving a third party for the recycling of metals into it's production costs makes this speculation even more patently absurd.
**edit - forgot to mention this**
The machining-out-a-billet process IS used in industry - but only for prototyping, or the construction of molds (for casting or injection/blow molding). Molds are insanely expensive to fabricate, so initial prototyping for objects is usually accomplished through carving and machining, or a form of rapid prototyping. Once design is finished and approved, molds are created, and then the final product is cast or molded.
** edit done
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Additionally, as a sidenote, I also highly doubt that the 'brick' refers to a Windows-smashing somethingorother. Firstly, Apple's marketing is consistently clever, and 'brick = smashing windows' is far too loose and random a metaphor to be plausible. Secondly, while the "I'm a mac / I'm a PC" campaign has been successful, I don't for a second believe that going toe-to-toe with MS is the central obsession of Apple's business strategy, and therefore it's doubtful that they'd expand the anti-MS marketing any further.
Apple knows that it's core differentiator is a consistent stream of well-design, contemporary objects of desire, that happen to also be highly functional and well integrated with each other. It's customer loyalty, and acquisition, are based on the premium nature of it's products, and the perception that there is constant innovation occurring that puts novel and *usable* (ie. not something as abstract as a manufacturing process) features in the hands of it's users before the competition can follow suit.
I'm definitely of the opinion that the 'brick' - if that rumor is even remotely true, and there IS a 'brick' - refers to externalizing connectivity features to the power supply (video connections, usb, fw, ethernet, etc). Either that or a new take on the Mini.
That's my $0.02.
