At its heart intellectual property is a kind of Platonism. That is not to say that the people who support the legal notion of intellectual property are themselves Platonists, nor that the laws were originally created with that idea in mind. However the fact that intellectual property laws seem to be trying to enforce some kind of Platonism on a world that simply doesn’t work that way is probably the source of their biggest problems.
By Platonism I am of course referring specifically to the world of forms that Plato hypothesized. In the world of forms each idea, each abstract kind, is an individual entity; and when we conceive of such ideas somehow our mind reaches out into that world of forms and connects us to them. If there really was such a thing intellectual property laws would be obvious extensions of the normal laws associated with ownership, because they would simply be asserting your claim to one of these forms. Obviously you can’t stop someone else from accessing the form you discovered, just as it is impossible to completely stop people from trespassing on your land, and so laws are created to keep other people from misusing your property. And, although such a picture might seem intuitively compelling, the world simply doesn’t work this way.* There is no world of forms, and thus to speak of owning an abstraction is nonsense, because there is nothing to own.
And because the world isn’t structured in this way intellectual property laws are naturally problematic. Intellectual property is just one kind of information. And thus by using that information to make money it becomes available to the public at large, who are able to copy it at no cost, since there are no inherent barriers to the duplication of information, unlike physical objects. For example, if my intellectual property is a piece of music, the only way to make money off that music is by letting people hear it. But if they can hear it they can copy it, and so enforcing my claim to ownership is nearly impossible. The only exception to this general rule of thumb is when the intellectual property in question contributes to the manufacture of some product (say a way to make some kind of chemical), but is not itself the product. But in this case there is no need for special intellectual property laws, since this information can simply be kept secret (certainly a better option than openly claiming it as intellectual property, which would allow those who are willing to ignore your claims to easily use it themselves). Another problem for intellectual property is that as time goes on people tend to invent better ways of sharing and copying information (for reasons of productivity, ect), thus making intellectual property harder and harder to enforce.
But no matter how much intellectual property laws may seem to be fighting an uphill battle against the natural order of things there are some who would justify such laws by claiming that they are necessary to motivate innovation. Now in most fields this is simply not the case. Artists have always created great art, even before it was a commercial endeavor. And when your intellectual property is some new kind of device usually being the first to market is enough of an advantage to encourage innovation. (Consider the iPod. Even though Apple didn’t protect their idea of a portable music player that stored its own songs the fact that they came out with the first practical device gave them a huge advantage. No one needed to give them a monopoly on the idea to encourage them to invent the iPod.) There is, however, one industry that does seem to need the protections that intellectual property offers, the pharmaceutical industry. If companies weren’t allowed to patent their drugs they wouldn’t have the motivation to invent new ones; the time and effort spent developing new drugs wouldn’t be worthwhile, as their competitors could simply make their own versions of any new drug. But, even assuming this is right, that isn’t a good argument for continuing support for the illogical intellectual property system, instead it is a good argument for providing extra support for the pharmaceutical industry. If we wished to encourage the development of new medicines (and I think we do) the government could subsidize the research of these companies, or pay them large cash sums for developing new medicines (say based on the volume of the drug sold, by any producer, in the first year). And both of these alternatives seem superior to allowing medicines to be patented, which makes many of them too expensive to be afforded by much of the world.
Thus I conclude that intellectual property is a bad idea because it is a) based on a misconception of the world, b) nearly impossible to enforce (and becoming more so over time), and c) the benefits of intellectual property laws can be achieved through other forms of government subsidies (intellectual property rights being one kind of government subsidy**).
* It is possible many people support intellectual property only because this Platonism is so intuitive. Our intuitions about ownership are developed by exposure to cases involving real objects, and so when we are later asked to consider if ideas can be owned our intuitions mistakenly lead us to follow our accustomed patterns, causing us to assume that ideas are objects that can be owned.
** I may have lost a few people here, so let me explain in more detail. Intellectual property rights grants someone an effective monopoly over the idea. This allows them to make more money off of that idea, money that comes from consumers. In effect the government is transferring wealth from consumers (in the form of higher costs) to the intellectual property owners. This is a roundabout way of simply taxing some members of the public and giving the money to the intellectual property owner.