Stealing means you are taking away something from someone, so that they no longer have it. So copying is not theft of any personal property, as that isn’t taken away.
What could next be argued is that copying is the stealing of revenue. In other words, where stealing makes someone worse off right now, copying makes them worse off in the future.
There are other ways of making someone worse off in the future. Consider two producers of similar products. One of them can lower the other’s revenue by:
Working harder and producing more, and then selling more at lower prices. Or by.. switching to a completely different kind of product. In the market, money can be spent on all sorts of goods, and more spent one place means less spent in another. Or by.. convincing people to change their habits. You can convince someone of desiring a less luxurious lifestyle for the sake of traveling more or spending more time with their children. Or by.. innovating. Creating products with new features or altogether new products can harm someone else’s revenue.
What an entrepreneur does is anticipate future consumer desires, and then he combines and transforms resources in such a way that he expects to gain a higher reward than he incurred in costs. It remains up to consumers to trade with you if they think it benefits them.
The process of taking goods and turning them into more valuable goods is a creative process. It creates a trading opportunity for consumers that did not exist beforehand.
In the market we find information that helps us in this process. We find prices of things we may buy as inputs and we find prices that people are willing to pay for products that we want to compete with. We also see what those things are that people like, in what way they are being sold, and where and when. All this information has come available through the free choice of individuals.
What is valuable to the consumer, what is an innovation in the market, is an improvement on any of the characteristics of the existing product offerings: price, quality, functionality, location, time, format, etc.
I want to argue that any information that is voluntarily exposed to the public should be free to copy by others. If you send out information into society then that responsibility is on you. If you don’t want that information to be used by others then you should keep it to yourself or treat it like a trade secret. This means that you contract with any person you give the information to that they keep it a secret.
Suppose your product is a book and you treat it as a trade secret. This means that bookstores cannot allow customers to browse through it without signing a highly demanding contract, that buyers cannot allow anyone else to see it and thus have to keep it locked up at all times, and that reviewers cannot talk about the content publicly at all. Such a business model is nonsensical for goods that you are trying to sell in large quantities and are easily copyable.
Entrepreneurship is a process involving unavoidable uncertainty; you cannot know if the profits of tomorrow will equal the profits of today. It is also the rational nature of man to improve his situation of tomorrow as compared with today. For both these reasons entrepreneurs continually try to improve on the cost of their production processes and on the value of their product offerings. It is up to them to find ways of recovering the cost of information intensive products voluntarily in the market, without resorting to the forceful hand of government power to threaten people who are doing nothing but offer consumers a product using information and techniques that were made discoverable voluntarily in society.
I have dedicated a subreddit to this idea: http://www.reddit.com/r/noip/