Here is a quick performance of two card transpo and just this simple trick freaks them out (warning has some cursing in it)

http://www.youtube.com/watch?v=bGQjlwnr9To

That's a fun trick! Great reactions!

This is one of my favorite card tricks to perform. It's simple as you said, but always gets great reactions. It truely seems impossible to the spectator. Eventually you may get a heckler that screams out "duplicates." What Iv'e adapted for this is a signature from the spectator. The effect gets that much better when they sign one of the cards. I even go as far as to say ,"I want you to sign this card, so we know there is no chance of using extra cards or duplicates or anything." Some may disagree, but spectators take our word for a lot of things. Good job.

Ron