Yepp I think it'd look good too if you forced the card numerous times, and had one central person take the card and not look at it, after EVERYONE has yelled the card, have them turn over the card they are holding...bam same card everyone yelled!
Or, in that sense, have one person come up and have them patiently wait.
Tell them that numerous people are going to randomly choose a card out of the deck.
Once numerous people have "freely chosen" a card, turn to the helper, and say you will choose a card, and with luck, it will match one of the cards that some one in the audience remembered.
Have them "choose" a card and hold it face down.
On a count of 3, everyone yells the card they chose! They are stunned, and then the helper flips over their selected card, and bam it is the same card that everyone yelled!!!!
Just a presentation idea