Where do creators get the right to deny others from copying their work?
Indeed, after a certain period of time creators lose that right, they are only granted it temporarily. Copyright law is just an arbitrary legal mechanism, not a "natural law" whose purpose is to help creators get paid (enough times, not every time) for their work (so that creators have the time and incentive to create). If there were other mechanisms available that ensured that creators got paid (as well or better then they are currently) that didn't restrict distribution or copying - we'd use them.
Many /.ers feel that alternate mechanisms are here or very close and, more importantly, that creative work should be a service rather than product-based industry. Many people, like Clay Shirky, understand that we've developed better solutions (digital networks and P2P, etc) to the manufacturing and distribution problems that copyright and copyright industries evolved to solve. What TPB is doing is legally dubious, but there is a great deal of sympathy for them because using TPB feels like what will be mainstream, legal practice in the future. The is no escaping the reality of digital networks and the shift to digital work as a service.
This change is inevitable because the freedom to distribute and copy is so immensely valuable to the world as a whole (this is already recognized even for physical goods which is why creators control over copying is already limited). In industries like software development where creative work generally results in valuable tools it has already been recognized that more freedom is (on the whole) more valuable then any temporary monopoly rights. i.e. Freedom to use/access/modify every other tool is more valuable then charging for access to your tools, especially when you are trying to make another tool. (*ahem*)
Obviously, tools != entertainment/cultural work but as the great Hans Rosling (http://www.ted.com/index.php/speakers/hans_rosling.html) said, "Culture is what makes life worth living." Applying similar freedoms to cultural work should see different but equal or greater value for all of us.
It isn't the end of the world to shift from products to services, and in the bargain you get freedom to (access, modify, redistribute) every digital tool that helps you create new tools and every digital cultural work that makes your life worth living...
1) Get paid for your services
2) Freedom to (access, modify, redistribute) everything digital
3) Profit!