Cryptoamnesia: why we have a patent system

From The Science of ‘Accidental’ Joke-Stealing and Plagiarism at nymag:

Imagine you were at a meeting last week about some kind of complicated problem to which you proposed a clever solution. Then the conversation moved on, no one picked up on your idea, a colleague presented a different solution and the decision was made to try that first. At the next meeting it becomes clear that the solution is not going to work. Fortunately your colleague has come up with a different idea in the meantime, a better idea, a brilliant idea: yours. You glance around the table. To your horror you see that you are the only person who realizes it was your idea. What has gone on in your colleague’s brain?