I wrote a thing about this a few weeks ago for the Magic Review Blog, and I concur almost completely with Mr Brushwood's thoughts on the subject. I think there are many advantages to exposure, and we just have to stop our Canute-like resistance to the inevitable tide of freely available information and learn to benefit from it. For example, does Derren Brown lose his impact because people believe he can "force" ideas on them? Not at all, he's made that into a crucial foundation of his performance persona. Would an ACR be less effective if people knew about the possibility of a pass or a centre deal? No, and in fact they would watch your multiple-lift sequence and marvel all the more at your astonishing ability to perform these moves so undetectably.
I like to think of exposure as giving a "glimpse behind the curtain". An analytical spectator with no knowledge of magic techniques will inevitably jump to a simple and prosaic explanation for your feats, "They're all the same card", "It's a trick deck", etc., etc., even if these don't tally completely with what they witnessed. If you've allowed them to understand some of the possibilities of magic techniques, you can raise simple effects to the status of a miracle. Dai Vernon described fooling Allen Kennedy with a double-lift, making him believe it was "a new kind of second deal". If Kennedy didn't have the knowledge of gambling sleights that he had, would this have been as effective? In the same way, we can learn to use the little knowledge of our audience to fool them all the more.
