In this paper, we quantify the potential gains of hybrid CDN-P2P for two of the leading CDN companies, Akamai and Limelight. We first develop novel measurement methodology for mapping the topologies of CDN networks. We then consider ISP-friendly P2P distribution schemes which work in conjunction with the CDNs to localize traffic within regions of ISPs. To evaluate these schemes, we use two recent, real-world traces: a video-on-demand trace and a large-scale software update trace. We find that hybrid CDN-P2P can significantly reduce the cost of content distribution, even when peer sharing is localized within ISPs and further localized within regions of ISPs. We conclude that hybrid CDN-P2P distribution can economically satisfy the exponential growth of Internet video content without placing an unacceptable burden on regional ISPs.