In copyright class we discussed the copyrightability of useful objects (e.g., lamps and chairs), objects that while serving a function and may simultaneously embody an artistic expression as well. The question is whether, and to what extent, these objects should be protectable by copyright. The argument for giving copyright protection to something like a chair is that if you are a chair maker, and you make a significant investment in the aesthetic appearance of your chair, it wouldn't be fair for someone else to be able to make and sell copies of the chair you designed without permission.
But "fairness" is not the thread that ties together American copyright doctrine. Economic incentive is. And here I don't see that providing copyright protection to a useful object - no matter how pretty - provides the economic incentive necessary to inspire their creation. Plenty of economic incentive exists without it.
For something like a book, however, there might not be sufficient economic incentive were it not for copyright. Without copyright, if just anyone could copy and publish the book without making the investment in creating it, the prospect of the author recouping the costs incurred in creating it would decrease, particularly because it would be much easier for the second publisher to undercut the price (the copyist publisher just need to cover the costs of replication, not of creation.) This inequity is referred to as market failure, and what copyright does is creates a legal structure so that the original investor - the creator - does not have to worry about having to compete against cheap reproductions. This protection plays an integral role in providing the economic incentive for creation of creative works, since without it there would not be one. People rarely buy a book because of its value as an object; its value comes from its contents, and that's what copyright protects.
However people buy useful objects - like chairs - because they are useful objects. They compete in a market of other tangible things, and get to differentiate themselves in this market on their many physical qualities. For instance the chair market includes consumers who will choose their chairs based on size, price, materials, quality construction, and many other factors of which aesthetics is just one.
In class it was argued that if anyone could copy the aesthetic design of an object it would discourage manufacturers from making the investment in aesthetics. Certainly any manufacturer needs to consider how much to spend on any one facet (design, materials, etc.) because it will affect the overall price of the final product, and likely, by consequence, total sales. But in addition to presupposing that figuring out how to copy an object's aesthetic design would necessarily be cheaper than developing one's own, the argument presumes that the aesthetic design stands on its own as a factor in assessing the value of the share, like a book, whose value is entirely manifest in its creative properties. But the chair still competes with its many other qualities - function, materials, and especially general craftsmanship - in the chair market, and thus there's no market failure for copyright law to correct.
Furthermore, imposing this extra level of legal protection where it is not needed can lead to unfortunate, counter-productive results. We have copyright in order to encourage the creation of works that we can use, but that very protection, when applied to useful objects, can inhibit our ability to use them as freely as we would like. To illustrate, one example that I raised in class was the shower curtain I once bought. I wrote about it here, noting how the manufacturers claimed copyright on it. (Actually, I misspoke in class because the copyright was only asserted with regard to the packaging. But it was a plausible hypo that the company would have tried to claim copyright on the shower curtain as well.) Claiming copyright protection is one thing; being entitled to it is another. It seems that manufacturers (like these) believe that because they made choices in what their product would look like, they should be entitled to protection because of it. However the law doesn't work that way: not all manufacturing choices are entitled to protection; only certain ones are. "Sweat of the brow" - mere effort - is not enough to earn copyright protection. There has to be something manifest in the effort that constitutes a work of authorship.
But even if we were to assume that there was sufficient authorship manifest in the design of the shower curtain (perhaps in its coloring, stitching, crease-patterns, floral design, etc.) to be worthy of copyright protection remember what I did with it: I made it into a Halloween costume. I transformed their copyrighted product. I made an unauthorized derivative work, an action that normally constitutes copyright infringement and could expose the infringer to a lawsuit.
Of course such a suit would be ridiculous (and possibly defensible, through the doctrine of fair use or other statutory mechanism available to consumers of copyrighted works), but that it would even be possible to sue people for interacting with the useful objects in their lives as they see fit indicates that this kind of copyright protection is neither justifiable or wise.
We use copyright as a means to encourage the creation of things to enrich people's lives, but by making people vulnerable to infringement suits for using and adapting the objects in their lives we've negated any benefit that the protection was designed to provide. Even if we agreed it important that some chair or shower curtain manufacturer has the extra incentive to make sure their products are pretty, and even if we thought copyright was the only way to provide it, surely that benefit pales against the suppression of the individual autonomy to use the things in one's life as one wants.