Just one counter example from my personal experience. I upgraded my Macbook Pro to 4 GB myself some time ago. Recently it stopped working so I brought it to an Apple Store. The serial number indicated the MBP was from a batch made with potentially faulty graphics chips. When I said the memory chips were not from Apple they said those chips would have to be tested to insure they weren't faulty. The memory chips were fine and the repair (replacement of the motherboard with 4GB which I assume were mine) was done as free warranty service. So if someone claims upgrading your memory chips voids your warranty, I'd have to say that person does not have all the facts.
But the RAM has always been user replaceable/upgradeable in Apple products, and the hard disk is now that way too. If Apple start using this in their computers, it will only be used on the seals that cover the more complicated parts, like the motherboard, CPU, and GPU. The bits that are easy to damage. RAM and HD are not easy to damage, and if you do, the damage is pretty obvious.
This device is not intended to prevent users from upgrading RAM and HD, but simply preventing people from getting into their computer with a soldering iron to kill it for warranty purposes.
Then again, it's probably not meant for Apple computers at all, just the iphone and ipod. And maybe the tablet.