It’s obvious why Viacom and its copyright lawyers want this change in the law: It would make their lives easier to pass the burden of enforcing their copyrights onto someone else. But innovators — and end users — wouldn’t be so lucky. It would be impossible for an Internet company to know when it had spent “enough” on copyright policing without taking its chances in court. And in the process of trying to satisfy this impossible burden, it would end up shutting down many of the transformative user-generated works like parodies that the law is designed to protect.

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True, Google today can afford to do these things. But the YouTube of 2005 could never have afforded those kinds of costs. And neither could the Google of 1998, or the eBay of 1995, or the Facebook of 2004. If Viacom prevails, it will be a crushing blow for small startups — the YouTubes, Facebooks and Googles of tomorrow. The message will be that you can’t play in today’s Internet unless you’re a big fish. And that would be a disaster for innovation.