“…[S]oftware isn’t just something new. Software is something fundamentally different. Abstract and slippery, it doesn’t conform to the ordinary constraints of the real world of objects. The nature of software has created not only a different kind of intellectual challenge, but a different kind of industry with its own particular economic structure. To this is being applied a 200 year old patent system.
…In most other industries, a product will contain perhaps twenty parts. In the case of sophisticated consumer goods, such as video cameras, we could raise this to 1000 parts. Nevertheless, the constraints of the real world ensure that the complexity of the product cannot become too great. Software, however, is essentially free from these constraints. A major computer program can comprise anywhere from 100,000 to 10 million lines of code. In most other industries a product will involve technologies covered by just a few patents. In the software industry, a product can contain thousands of inventions, any of which might be patented.”
From article at League for Programming Freedom