So, call me a pessimist but this 'feature' seems to just be a gateway into requiring Apple to approve the resale of any piece of hardware they sell.
"Want to sell your iPhone? Sorry, can't do that without entering the originally registered email address / Apple ID that came with it. Oh, by the way-if you want to update that info its a nominal $25 fee. Oh, did I say $25? I meant $250. OR! You could trade it into us for a new, unsaleable product.
:) If you trade it in, we'll take $275 off your next purchase of $600 or more. Aren't we nice? Look, you have options." http://www.bloomberg.com/news/2013-06-06/apple-said-to-start-trade-in-program-to-boost-new-models.html
And, speaking of security--isn't the adage that there is no security without physical security?
How will the phone know it's correctly associated with the right ID? Will it not either a.) cache credentials from a remote login to Apple ID, or it will b.) require an internet connection? In either of these cases it seems it'll be possible to unlock the phone with the correct info--and then proceed to spoof whatever information is necessary to get access to the base system.
With security exploits all bets are off on what the software is expected to do.