YouTube is not automatically a copyright risk, according to John Palfrey, speaking to WSJ, because it’s not Napster:

The thrust of the business is not to encourage anyone to violate copyright, but rather to create works that they then can distribute online. The business model that YouTube features is a far cry from any of the early music file-sharing businesses. That difference in business model should make a big difference in terms of the copyright risk calculus.

Makes sense to me.