Are Software Patents Evil?

Patent trolls are companies consisting mainly of lawyers whose whole business is to accumulate patents and threaten to sue companies who actually make things. Patent trolls, it seems safe to say, are evil. I feel a bit stupid saying that, because when you're saying something that Richard Stallman and Bill Gates would both agree with, you must be perilously close to tautologies.

Are Software Patents Evil? is (another) well-written essay by Paul Graham. (It even uses hockey as a metaphor!)