File sharing, typically involving video or audio material in which copyright may persist and using peer-to-peer (P2P) networks like BitTorrent, has been reported to make up the bulk of Internet traffic. The free-riding problem appears in this "digital gift economy" but its users exhibit rational behaviour, subject to the characteristics of the particular network. The high demand for the Internet as a delivery channel for entertainment underlines the importance of understanding the dynamics of this market, especially when considering possible business models for future pricing or licensing regimes and for the provisioning of network capacity to support future services. The availability of specific titles on file sharing networks is the focus of this paper, with a special emphasis on the P2P protocol BitTorrent. The paper compares the incentives provided in BitTorrent to those in other file-sharing communities, including file hosting, and discusses the number of titles available in the community at any given time, with an emphasis on popular video items with ambiguous legal status.