"Intellectual property" has become the international household term denoting the rights addressed in Part II of the TRIPS Agreement. The term suggests that such rights grant their proprietor an entitlement to exclude others from using the protected subject matter. However, in reality, intellectual property has never been exclusive in a strict sense. Copyright, in particular, is relatively rich with examples of rules allowing third parties to use protected content under certain conditions, and against payment of a fair remuneration. In economic terms, this means that property is replaced by a liability rule. After explaining the basic tenets of property vs. liability rules and commenting on the factors informing the choice between the two types of rules, the article gives an overview on liability rules which can be found, or are under discussion, in the various fields of intellectual property. It is argued that although liability rules may pose specific concerns with regard to administration and efficiency, their fundamental rejection as regulatory model would have no rational basis. "Intellectual property" is a term of convenience rather than enunciating a truth cast in stone, and the practical relevance of liability rules is likely to increase in view of challenges by novel forms mass uses of protected content, and by growing sophistication of technology.