[A US Professor estimates that he could have $4.5 billion in copyright liability in a single year](http://arstechnica.com/news.ars/post/20071119-overly-broad-copyright-law-has-made-us-a-nation-of-infringers.html).
And that’s without trying very hard. He’s probably overstating his case a little (it’s not *that* typical a day he uses for his calculations). But the basic point is clear – copyright law is insane and massively out of sync with community standards.