An interesting article. It has some problems, though.
The title page misspells Michael Weber's name (as does footnote 150 on p. 31), and page 23 misspells Norman Gilbreath's. Page 2 errs in the title of the most important book on sleight of hand with playing cards ever written (see footnote 11). "Musicians and authors, for instance, work with a versatile, but limited palate" that should be "palette". And the inventor of patented coin magic gimmicks is "Pressley", not "Presley", Guitar (see pp. 16, 17, and 19). But these are nitpicks, and are (perhaps) reflective more of poor editing than of the content of the article. Moving on to that . . .
He defines three categories of magic tricks that comprise the "vast majority" as those depending on apparatus, depending on sleight of hand, and tricks which are "self-working"; leaving out tricks that are wholly dependent on misdirection (card under glass, for example, or the Twisting Arm Illusion).
He alludes to other creative fields, such as fashion design, cooking and dance, in which intellectual property is protected less strongly than artists and creators may like, but omits the performance art which may be most closely related to conjuring in terms of intellectual property rights stand up comedy (see, for example, Dotan Oliar & Christopher Sprigman, Theres No Free Laugh (Anymore): The Emergence of Intellectual Property Norms and the Transformation of Stand-Up Comedy
, 94 VA. L. REV. 1787 (2008), online HERE
Any discussion of Trade Secrets with respect to conjuring that fails to mention the Fitch-Kohler Holdout and its creators' use of contracts and Trade Secrets to protect it (so far, apparently, with success at least, I've never heard of anyone divulging the secrets) seems incomplete, at best. No other trick in recent memory has been so aggressively, yet publicly, discreet (although the Real Secrets Trick of the Month bears watching).
He discusses Utility Patents at some length, but ignores Design Patents. The overt, external design of tricks such as Harbin's original Zig Zag Girl may be equally important to the successful creation of illusion as the covert, internal mechanical workings.
He glosses over the the very real problem that when a magician's proprietary material is undisputedly stolen, the costs of pursuing grievances within the courts may far outweigh the actual losses, or what may be recovered. See, for example, the New York Times
article (27 Sep 2006, p. E1) about Eric Walton lifting material from Ricky Jay's "52 Assistants" and "On the Stem" shows, in which Jay said, "I paid for a ticket and I sat through the show, and I would very much like my money and my material back."
Some magicians do not want to preserve secrecy or control the manufacture or use of a magical invention, but rather desire only credit for inventing it. The Statutory Invention Registration may be of use in such circumstances. Feldman does not discuss SIRs.