I seem to think that ianzin has a personal stake in this. Are you an illusionist? All of your counterpoints seem to revolve around who has the right to commercially exploit information.
The thing is, information isn’t copyrightable. No one has an exclusive right to knowledge.
Here are some examples of protections that are valid on the USA. It’s not all inclusive:
Copyright - verbatim reproductions This covers printed matter, recordings, digital information. The copyright holder can prevent verbatim reproductions. Unless someone makes direct copy from a copyrighted source, this just doesn’t apply to any magic trick in existance. Copyright does not inhibit my ability to paraphrase. This gives me the right to convey any information that I want for any purpose, unless explicitely prohibited by law (e.g., how to build a nuclear bomb).
Copyright - performance As you mentioned, Teller’s “Shadow Rose” trick could be copyrighted (I don’t know this, but I’ll assume you’re correct). This validly prevents me from performing the trick without royalties for commercial gain. Kind of like not being able to sing “Happy Birthday” at a restaurant. But there’s nothing in the copyright provision that prevents its fair use, such as me demonstrating it to a friend. There’s additionally absolutely nothing preventing anyone from disseminating the information – the copyright is only for public performance.
Intellectual property – everything’s intellectual property. There’s no legal protection for intellectual property. It’s up to you to either (a) maintain it as a secret, or (b) protect via the patent and trademark system. Any not so protected is public domain.
Trade secrets – Again, what’s a trade secret, and what’s the legal theory that protects a trade secret? There is none! Again your only protection is the trademark and patent system. There are court cases, though, that establish that a company that benefits from someone’s breaking an NDA are liable as if they broke the NDA, but the liability is only affected by any commercial advantage that was taken – no harm, no foul. You all know that DeCSS is now finally legal; not because of any inherent rights, but because there’s nothing that protected it legally from reverse engineering.
Patent - design Ah ha. This is what lets Apple patent the design of their wire wastebasket in OS X. It doesn’t protect the metaphor, but rather this particular image. I can’t really think of an application of this towards telling a magician’s secret, though.
Patent - utility This is about the only thing that a magician could pull to prevent others from performing his trick. Of course this makes the method behind the trick public information. Information, as we know, is public domain. So even if the trick were patented, we’d have the right to know how it were done, even if we couldn’t commercially exploit it. I’ve not looked at the P&TM site, but I’m positive that there are magic tricks or magic apparatus registered there. And it wouldn’t be illegal not unethical to post about them or link to them.
Non-disclosure agreements (NDA’s) This is something founded in contract law and not copyright and trademark law. This means that a magician, to preserve his secret, can make his assistant or whomever sign an NDA. If the person violates the NDA, it’s just too bad for the magician for not having protected his secret with a patent. Although, as mentioned above, if the NDA violator makes the trade secret available only to another company for commercial gain, then the other company (other magician) could possibly be held liable. If the information is released publicly, then it’s public domain. Information is free/gratis. Again, in a non-criminal sense, the NDA violator can be subject to a lawsuit.
This one for the mods: can I offer civil indemnity to the SDMB for the purpose of allowing a single, offsite link to a free webpage that describes in the authors’ own words how this original magic trick is done? Fax me the paperwork. I’ll risk the lawsuit. How much can the damages possibly be?