secondary The Regulation of Last-Mile Broadband Networks markets must be concentrated and protected by entry barriers before vertical exclu- sion can plausibly harm competition. Our foregoing discussions of the natural monopoly and network economic effects justifications for regulating last-mile broadband networks demonstrate that these structural preconditions are not satis- fied. Indeed, the D.C. Circuit emphasized the emergence of intermodal competition between cable modem and DSL providers when striking down the FCC's Line Shar- ing Order. The availability of broadband access from other providers meant that the dangers of vertical exclusion were not substantial enough to justify incurring the costs of mandating UNE access to the high-frequency portion of the loop (U.S. Telecom Ass'n, 290 F.3d at 428-29). The FCC drew the same conclusion when elim- inating line sharing on remand and refusing to mandate UNE access to the hybrid copper/fiber loops used in DLC systems (FCC 2003d). The FCC drew similar conclusions in the Wireline Broadband Internet Access Services Order, which eliminated the Computer Inquiry rules with respect to last- mile broadband technologies used to provide Internet service. As the FCC noted, the broadband market is characterized by vibrant intermodal competition between cable modem and DSL providers. In addition, those providers faced the real prospect of entry and increased penetration by satellite, fixed wireless, and other alternative transmission technologies. In the face of such competition, last-mile broadband providers have little to gain from engaging in vertical exclusion. On the contrary, the FCC concluded that the desire to spread fixed costs over the largest revenue-base possible gives them powerful incentives to maximize the traffic on their networks by accommodating as many unaffiliated content and applications providers as possible (FCC 2005d). In addition, an economic consensus exists that vertical integration and vertical restraints can yield substantial efficiencies that mu