ions that are necessary for vertical exclusion to be plausible. For example, as noted earlier, the Court recognized that "the indispensable requirement for invoking the doctrine is the unavailability of access to the 'essential facilities" and the doctrine "serves no purpose" when the input in question is available through other means. In SO holding, it implicitly recognized that proof of a monopoly over an input is a necessary condition for stating a vertical exclusion claim. The emphasis on monopoly power is further reinforced by the Court's concern that forced cooperation with rivals also risks becoming a focal point for collusion. In addition, the opinion accepted the reading of Spectrum Sports discussed above when it underscored that any claim that a monopolist is attempting to use the leverage provided by its monopoly to attack a second market must show "a 'dangerous probability of success' in monopolizing [the] second market" (540 U.S. at 408, 411, 87 Campbell and Sandman (2004); Lopatka and Page (2005). 88 MetroNet Servs. Corp. V. Qwest Corp., 383 F.3d 1124, 1132 (9th Cir. 2004). 89 Fox (2005). 90 Areeda and Hovenkamp (2008c). Antitrust as Applied to Network Industries 415 n. 4, quoting Spectrum Sports, 506 U.S. at 459). This language has been widely interpreted as requiring proof of market concentration and entry barriers in the secondary market before a monopolization claim will lie. 91 Read together, this language represents a sweeping acknowledgement of how compelling access to bottleneck facilities may impair economic efficiency. When alternative sources of supply exist, simply allocating the resource that exists is not the best solution. The better course is to allow any supracompetitive returns to serve as the signal and the incentive for others to develop independent sources, which in turn will provide sustainable benefits to consumers without the continuing oversight of the terms and conditions of sharing by antitrust courts. 2. The Allocation of Authority between Antitrust Courts and Regulatory 