Just realized the fact I type like an American online (I'm British) would confuse someone for a little bit if they tried to de-anonymize me... (although they probably wouldn't struggle anyway)
I REALLY love this idea. The way that this could combine the tactile nature of physical games with the benefits of digitization is awesome. The example you gave somewhere of the vampire card is so cool.
Yes, they're linked by some form of government ID. Of course, it's probably very easy to get around that in some manner by just playing offline games or using a parent's ID.