If we privatize the enforcement of contracts, let those who wantto "own" ideas pay for the enforcement of that contract. Market forces will probably lead computer programmers to tie a perceived value to the registration of the program (cheap upgrades, technical support, etc.); rather than paying for a protection agency that tries to police the digital information realm. But they would be welcome to try to enforce a contract against copying a program that the purchaser would sign when he buys the product. I just wouldn't subscribe to a protection agency that used some of my subscription fee to police copyright protection.
Any service or good has, as a component of its' cost of production, not only the costs of labor, marketing, capital, etc., but also the cost of exclusion. For the owner of a movie theater, these exclusion costs include paying for walls, ticket windows, ushers. These serve to exclude or fence out 'freeriders'. Now they could set up projectors and show the movies on low level stratus clouds (ok, screens in parks), and then attempt to prevent casual passerbys from watching. The method of marketing their product is their choice. In the case where their marketing decision results in the publicness of a good, it seems to me to be grossly unjust to ask the government to force all who might potentially see the show without paying to kick in some bucks, whether they DO in fact see the show or not. Or to force passerbys to don glasses that prevent them from viewing the movie. Yet the proponents of property rights in ideas choose such a method when they attempt to get every person purchasing a blank tape to pay a royalty to a third party. Alternatively, as with DAT tape recorders, their proposals seeked to ban or cripple entire technologies. This method, done in the name of preventing technologies which are capable of recording publicized (broadcast) music without loss of fidelity, would have made mere ownership of tangible property (DAT recorder) a crime. I view proposals for such an implementation of property rights in ideas, which wipe out other areas of property rights altogether, as inconsistent.
IMHO, you can't really "own" ideas. You can imbed your labor in tangible property and try to exercise property rights over that, but claiming ownership of ideas is a reach.