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Also, it's possible that whatever chipset Apple is using can not utilize more than 4GB of RAM.

Thanks, I think this answer helps me understand why 4GB is the max. Size constraints didn't seem logical to me since there are surely 8GB RAM the same size as 4GB RAM that are available for Apple to use within the Air, I just couldn't put my finger on what else would be holding it back to only 4GB.
 
How does their website agree? I don't see anything implying it's possible to get anything but the stock 2GB model, much less upgrade it by hand. I don't even see 4GB models offered, so even if the "upgrade" is in fact a different computer, Best Buy isn't prepared to offer it.

I guess you didn't even look at their website? :rolleyes:

•2GB DDR3 SDRAM
For multitasking power, expandable to 4GB.
 
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