They're just cards... but actually the ones your find at Walmart a bit different. The finish seems a bit off and it doesn't come with a double backer.
Maybe you got ripped off, because every deck I've bought at Wal-Mart comes with a double backer.
But yeah, there's really not a lot of difference. The only difference is that with the batches sold at Wal-Mart, Theory11 doesn't do quality control on them (as in, it doesn't pass through Theory11's hands), and I believe they get printed on different machines (machines intended to handle a much larger volume of cards). Not a big deal, in my opinion, because if there
are any issues with the quality, the USPCC will replace the deck (or defective cards) for free anyway.
And as for them losing this mysterious "specialness"...all I have to say is: Huh?!
Edit: Oops, forgot the stock as well. They
are mighty different, heh. But still...regular Bicycles are good enough for me, so having Guardians with the stock of a regular deck of Bikes doesn't bother me one bit. I kind of prefer Bicycle stock, to be honest. It doesn't last as long, but it feels better to me. Probably just a personal thing.