i don't see how if anyone who wasn't specifically looking for a buried code would even begin scanning it. and even if they were scanning it, they'd have to have the card fairly motionless and up close for quite a few seconds. it took me 1-2 minutes, looking for something, and looking specifically in the top left and bottom right corners, guessing that's where it would likely be. you give me only a few secs, at a distance, as part of casual trick, no way.
unless you're trying to fool other magicians, who know exactly what they're looking for...
p.s. i always thought it'd be fun to play poker one time w/ my buddies w/ a marked deck. we only play for little money, to keep it light, but there's ALOT of talking smack, and it would be so much fun to just burn them. are those kind of decks easy to find, seventh?
the only problem is, you use it once and let 'em know what you did, they'd never trust your decks again n would probably bring their own ever after... ohwell, it'd still be worth it...