One of the biggest problems with the patent system - and to a lesser extent with copyright - is the use to try to tax other people's innovations by claiming a monopoly over something you didn't invent. This is the heart of what it means to be a patent troll (see the article below about banks), and why it blocks rather than promotes innovation. There is a nice posting about SCO on Economic Logic: the point is that SCO now exists as a company the sole purpose of which is to slow down progress by claiming IP rights over other people's inventions and creations.

In response to the blog post David cites, I left this comment:

Patents increase rents by shielding patentees from the competition that would reduce them to competitive levels. But they do not in and of themselves create rents, which are the result of innovation and the market process. To say that patents can be abused is like saying that slaves can be abused. Well, yes, but isn't slavery itself a violation of a slave's natural rights to life and liberty? If this is true, then patents are also a violation of the natural right of non-patent holders to use their own lawfully obtained and sometimes independently created copies of patented inventions and processes. SCO is not merely an abuser. It is also a monopolist.