ond situation arises when the government physically takes less than the fee interest in the owner's property. For example, the Court in United States V. General Motors Corp., noted that although the government need not compensate for a property's going-concern value when it takes the full fee interest, "[i]t is altogether another matter when the Government does not take [the owner's] entire interest, but by the form of its proceeding chops it into bits, of which it takes only what it wants, however few or minute, and leaves [the owner] holding the remainder." Because only part of the property was taken, it was effectively impossible for the property owner simply to reestablish its business elsewhere. In such a case, the proper measure of compensation is not just the cost of the property taken, but also the going-concern value of the property as reflected by rental fees that could be obtained on the open market (323 U.S. at 379, 382; see also Kimball Laundry, 338 U.S. at 7, 14-16). These situations underscore the constitutional problems that would result if network access rates were based solely on direct cost and support rates that reflect the probable demand for network services. To the extent that compelled access to any particular portion of a network is justified, it must be because that portion bears natural monopoly characteristics. Because it is infeasible for the network owner to establish similar facilities elsewhere, the physical occupation of its facilities requires that the owner be compensated for the going-concern value of the property taken. In this case, the value of the property is reflected by the value of the network services provided. In addition, the partial nature of the physical taking effected by access requirements provides yet another reason for requiring the government to compen- sate network owners for lost profits. Access necessarily involves a physical taking that is considerably less than the full fee, thus interrupting the owner's use of the prop- erty and leaving it inextricably i