The case against YouTube

With that as a given, however, courts must also take into account the second point: Providers of a new technology will often be tempted to attract a customer base by allowing copyright infringement. What better way to draw users to your new video website than to offer, at no charge, clips that users already want to see? To counteract this, the law must demand reasonable precautions both at the design and operational stages of a technology.

Exercising care is not a Herculean task. YouTube, for instance, has enormous information about what search terms its users enter and what tags posters submit when they turn in a new video. That information could be combined with public data about characters, names and movie titles to easily identify videos that might need to be reviewed by a copyright lawyer or run through an automated system that compares suspicious clips to known copyrighted work. Perfection is not required. Cost-effective filtering technologies are.

Finally, bad intent on the part of providers must be mercilessly punished. By necessity, copyright rules in new-technology settings are flexible and imprecise. They allow creators of new technologies to experiment with design and implementation. They excuse small, innocent mistakes. But that flexibility cannot be entrusted to people or companies that knowingly exploit loopholes. This is why the last big copyright fight -- the music industry's case against Grokster -- proved so simple. The question of exactly which precautions the law should demand of Grokster and related services was a difficult one. The question of whether Grokster's ill-motivated founders should be allowed to play any role in establishing those rules, by contrast, turned out to be embarrassingly straightforward.

Admittedly, even guided by these three touchstones, copyright law will struggle mightily when it comes to defining the permissible legal contours of the YouTube service. Recently, for instance, YouTube introduced a feature that allows users to limit the audience for their videos to pre-approved friends. That might be an appealing feature to the extent that it allows Grandma to share her vacation videos with the family without showing them to the whole world. But it poses a challenge for copyright holders who obviously cannot monitor videos they cannot even see.

This reinforces the importance of the three touchstones. Copyright holders cannot be armed with too powerful a legal remedy because even a well-meaning technologist might on occasion innocently misstep. At the same time, those who own and operate a new technology must feel constant pressure to account for the copyright implications of their decisions.

And, above all, copyright law can welcome only those with pure motives. Those who abuse the law's caution have no claim for its mercy.