This whole subject came up once again for me, when I was reading how ARIN is trying to "capture" (contractually speaking) the legacy owners of IPv4 address space. These are people, presumably including amprnet, who received their allocations well before the current Internet bureaucracy was established. An interesting look at the issues is available in ComputerWorld. (Thanks slashdot!)
The amprnet allocation usage must be tiny in percentage terms, and hard to justify in a world of address scarcity. Standalone radio networks based on TCP/IP (if there really are any!) are likely based on VHF if not 2.4 GHz (HSMM), and they are fundamentally local or regional and are not likely to be routable from the Internet. They could probably equally well use a network address like 10.0.0.0/8.
In recent years, various other network-based amateur systems have developed, including EchoLink, IRLP, D-Star, winLink, etc. These make effective use of Internet links, but have no particular need for the amprnet addresses.
I don't want to argue the pros and cons so much as to point to the odd situation of our hobby holding such a valuable resource, with no visible institutional support.
What are the chances to get a little more RF spectrum, if we hand back the IP addresses?