Perhaps there is better wisdom out there on correct metrics for these values. From my limited viewpoint, the only way to recover the space is a voluntary return, based on the original allocation policies.
There must be some mechanism implemented whereby address space will return to the IANA after a specified period of time unless otherwise requested by the prefix holder. Otherwise what will happen is that this 60% (or some other large percentage when the figures finally settle) of the 192/8 address space will effectively be lost from the internet with no real means of retrieving it. A system like this without any garbage collection mechanism is eventually going to fill up with defunct allocations and the cruft of years past -- something which is not an option when dealing with limited address space.
as a technological means to protect a networks internal stability, is presumptious and rude at best and legally indefensable at worst.
How are the InterNIC coping with the new domain name charging scheme? If this were successful, a similar scheme might be considered for address prefixes. The legal consequences are similar if not quite the same, and one is really no more rude or presumptious than the other. Nick