If there ever was a case that illustrated why software patents are idiotic, it is a story from today's slashdot. In a bold move, a company has filed a patent claim for linked lists.
Just to recap for a moment - patents are meant to protect new inventions, so that when you make a brilliant new discovery, like say, the light bulb, and someone wants to take that idea and get rich you can say "hang on, I was first, if you want to use the idea you'll have to license it from me".
Linked lists are as old as computer science itself, however. No, scratch that, they're a fundamental principle, in fact. They are what the Pythagorean theorem is to mathematics. The patent claim in this case is not for linked lists in general, it's for lists linked in more than one direction, which is just a common variant of linked lists. But here's the kicker, the patent was granted. That means the data structure I was taught in college (and which every comp sci student is taught) is now to be considered hands off. :( So if I write an application using linked lists, I am liable for patent infringement. It's a good thing patents are not backwards enforcable, or my old assignments in college would come into question. :lala:
Software patents, of course, are only applicable in the one country crazy enough to accept them, the United States. The idea was rejected by the EU some time ago, but another round of lobbying over patents in Europe is on the cards.
The point of a patent is to protect innovation. In this case, the holder of the patent is able to sue any company or individual for using linked lists, but that kind of case would be completely useless, because of the prior art principle. If a patent is granted and it is then proven that someone has used the idea before the patent was issued, then the patent is invalidated.
Other ideas already patented are Adobe's tabbed window panes (as used in Photoshop) and Amazon's one-click shopping.
Unlike DRM, patents are not such a big consumer problem, they apply more to developers. But it means that if a company is granted a patent for "lossy compressed music files" (mp3), and uses this idea in a program (Windows Media Player), then anyone else wanting to play back these mp3s can't, in any way, make this happen. Because the limitation isn't on the format itself, it's on the idea that such a format can exist. So noone can even come up with a different format for music files, the whole thing is restricted. This is not a good example, because a) there's lots of prior art for music compression and b) I took this from thin air, so it may not be that realistic or representative. Nevertheless, this is how the mechanism works and so for open source software, which often strives to provide alternatives for common commercial software, software patents is a minefield.