[modernerd]

Something to do with multiple Apple products being cut from the same sheet of aluminium to reduce waste, perhaps? From Ive's comments in the Objectified documentary:

'This is the bezel for the iMac. When we remove the aluminium from the display in the centre here, we actually take that material, and then we can make two keyboard frames from it.'

[2min30 into this clip: http://www.youtube.com/watch?v=YdVG4LcoY4Y ]

[tesseract]

I thought the iPhone frame was steel. Besides, even if the materials were the same there'd be a kerf.

[blackguardx]

Machining doesn't work that way. The groove in the laptop is done with a round nosed end-mill. It makes the rounded profile and creates lots of chips. Those chips are then melted down and made into something else by some other company.

[tesseract]

Machining still doesn't work that way, but on the Air the cutout goes all the way through so there is no need for a round nose mill specifically.

[blackguardx]

Sorry I haven't seen one. I only have an aluminum macbook

[ubermoe]

This explains that coincidence.

[nchlswu]

I think it is directly tied to this process; but it's definitely something deliberate (and I assume thought out for a while) as well.