Here's a question, has anyone who has received the device (or it's out for delivery) noticed that their N7 was added or linked to their Google Play account automatically by Google? Is that what is supposed to happen if you chose to link the device upon preordering?
My N7 is on the UPS truck, somewhere in my town today. I recall clicking "yes" to a question about linking it to my account, during the ordering process. When I look at my Play account now, I don't see it listed as one of my devices. However, I think that will change as soon as I get it and turn it on.
I think the linking only puts your email in it, then you log in to link it. Otherwise you'd put your email and password. In short linking it only saves you typing your email address once. That's the way the Kindle Fire worked at least and I know mine isn't on my devices yet in the play store.
There's no way they'd send them fully linked (as in the password already in them.)