In keeping with the season

Here's an April Fool's Day piece on joke-stealing, social norms and intellectual property (via Mark Thoma):

...Comedians have rules of their own about joke-stealing. And they impose their own punishments on thieves... Why do comedians do this? In part, because they live in a world where intellectual property law – in particular, copyright – does not help them much when a rival comedian steals a joke... lawsuits are simply too expensive and uncertain to work as an effective response... Today’s comics are intent on enforcing ownership rights. Yet they do so via social norms – informal but nonetheless powerful rules enforced by comedians on their peers... Comedians maintain a small list of commandments that every comic must follow – or risk being ostracized, boycotted, and sometimes worse. These norms track copyright law at times... More often than not, however, the norms deviate from copyright: for example, copyright protects expression but not ideas, but comedians’ norms protect expression as well as ideas...

I might quibble with the definition of social norms as rules enforced by fear of reprisal, but that's a minor point and, given my previous comments about Freakonomics, I have to give credit where credit is due.