Taking a breather from arcane copyright doctrine, here's an issue that's not specific to copyright, or even to law at all. What is the proper role of anecdotes in making policy arguments?

Suppose that I'm arguing that the term of copyright is too long, and I say, "because of Congressional pandering to special interests in Hollywood, even 'Happy Birthday to You' is still under copyright!!!" Why is this example likely to carry particular persuasive force? In part, because the audience probably makes false assumptions. "Happy Birthday to You" is one of the few songs that most people still learn as children, at home, from family and friends, far from the commercial world of iTunes and Vh1. That will cause many people to lump it with songs like "Mary Had a Little Lamb" and "Twinkle, Twinkle, Little Star," though the latter are considerably older. And many people may also assume that if "Happy Birthday to You" is under copyright, the copyright owner could demand a license for singing it at a family birthday party — outrageous! — though private performances have never been regulated by copyright. I discuss this sort of problem with the use of anecdotes in my article, I can't say that I have the answer.

Taking a hard line, one might say that all anecdotes and examples should be accurate and typical (and not foreseeably misleading) or they shouldn't be used. The requirement of being typical may be impossible to meet, however. Members of a group may be diverse enough that none of them is really "typical," and anecdotes can be misleading in very subtle ways.

Meanwhile, we human beings may be built in such a way that statistics often don't move us enough to take appropriate action. Specific examples, as supplements to numbers and percentages, may actually be necessary to engage us to respond adequately. So it's not clear that minimizing the use of anecdotal argument would even theoretically be optimal, given that we are who we are.

Here's a possible rule of thumb: small deviations of examples from the typical are inevitable, and just need to be accepted; medium-sized deviations should be accompanied with a proviso ("not all cases are like hers"); atypical examples should be avoided; and there should be some effort to figure out how typical an example is deploying it. I'm not sure how far that gets us, however. I have to confess that in yesterday's post, I mentioned the use of "Happy Birthday to You" in the movie "Annie's Coming Out" in part because the scene sounded striking: kids with multiple sclerosis were singing it to another kid with multiple sclerosis. Is that a typical use? Is the fact that that scene is touching something we should really take into account when formulating copyright policy in general, or in a fair use analysis?

Perhaps Volokh Conspiracy readers have insights to share.