I broadly agree with Paul Graham's essay on Software Patents, but I do think he underestimates the damage from patent trolls, and from what he calls the mafia-like behaviour of some patent holders.
Paul has been lucky in the field he has worked in, but in the Audio and Video area there are many patent thickets. Perhaps it is the history of Farnsworth's victory over RCA that makes video engineers patent hungry.
My first startup, The MultiMedia Corporation, was a spin-out from the BBC in 1990. One of our products was a program called MediaMaker that combined video from tape or videodisc, CD Audio, Pictures, digitised audio and Director animations into picture icons on a timeline for making presentations. It was demoed on stage at Macworld by the CEO of Apple, and we got Macromind to publish it.
Then the patent troll showed up. A company called Montage had made a video editing system that included several video monitors showing edit points from tape. The company had gone out of business but a lawyer had bought up the patents, including one on using a still image to represent a video sequence. The troll was working his way round the video companies, and he caused enough trouble to stop work on the product while we worked on a legal defence instead.
Later, while I was at Apple on QuickTime, there was a steady stream of patent trolls claiming that Apple should pay them royalties; enough to keep several lawyers busy, and a lot of engineers spending time working on prior art evidence demonstrations.
Several potential features were excluded from QuickTime due to patent thickets. The obvious one was the Unisys LZW patent that encumbered GIF, but there were other more subtle pressures that meant adopting open source codecs was discouraged. Working on the patent license agreements for MPEG meant that technology ready to ship was deferred pending legal agreement on more than one occasion.
So I'm much lass sanguine than Paul about this. I think software patents should not be granted, and the European Union's banning of them is the right decision. I hope the Gowers Review in the UK makes this UK law as well.