I'm in agreement with Curt. While the Invisible Deck trick is one of the greatest card tricks devised, it's also terribly simple to perform and the gimmick has been around for close to a century. Just as we sought out the knowledge to become magicians, so can anyone else, whether it's posted on YouTube, read in a book or viewed in a DVD or a download from a magic site. The knowledge has always been there, and always will be there.
But knowledge alone isn't enough. A person can know what a double lift is, but can they perform one convincingly enough that they aren't detected? (I've done triple lifts in the past to disguise a double lift - it's a riot when they think their card is second in the deck and it's not.) Can they do the other countless sleights of hand that take months and perhaps even years of practice to do smoothly and undetected?
If all someone wants to do is poke holes in a magician's act, they were able to do that long before YouTube and the Internet existed. Certain personality types can't stand being fooled and want to know how everything around them works. They want to show off their "superior" knowledge by poking holes in a magician's act mid-performance. That's not a big deal, really - because all they're doing is showing off how much of an ass they can be in front of an audience. I've dealt with this before - the solution is pull a new weapon out of the bag that they can't simply explain away. (Or smack them in the head a few times with a rubber chicken - whatever works...) If they can poke holes in your act, make your act BETTER.
Most people enjoy more than just the knowledge and the skill - they love the performance. I could do sleights and tricks all day for people by rote like an automaton and bore them to tears with it, but toss in the right patter, weave a little story into it, maybe a dash of comedy (like when I rub a card to put a little "magic" on it and it practically sounds obscene), that is entertaining, and no magic video or book can truly teach that, and that's what the audience really wants to see.