He is not demonstrating great feats of memory - he's performing card tricks; although he IS very good at it. If you watch the comments, every now & then someone will leave a comment revealing the secret and/or which book teaches you how to do it. Although those posts don't usually last very long - the YouTube mods remove them as quickly as they can.
The ironic thing about it is - there really ARE people who can memorize a deck of cards (though nowhere NEAR as fast as within one quick riffle). One very notable person with this ability is none other than Jerry Lucas, the ex NBA star from the 60's & 70's.
