These addresses were allocated in the age before The Great IP Shortage. There were no signs that the internet would be used privately by regular people and many sysadmins were clueless as to how IP networking worked. NAT routers were incredibly expensive and the right way to go was to just buy an IP block, distribute it globally across branches and use the router to block traffic from other IP blocks. All major companies in the eighties bought IP blocks, see http://en.wikipedia.org/wiki/L... . Ofcourse many more companies have settled with 'just' a bunch of class B networks as 64k hosts is not enough if you're aiming to dominate global business. I can actually understand companies like Ford or US Postal to register an A class. Others such as Eli Lily or the UK Gov Dept of Pensions really don't need so many adresses. But now the internet has changed and there are barely enough addresses for all existing devices. So these blocks should be revoked and private networks should be private.
Perhaps a nice rule would be : if you want to have a single public IP adress you will need to be online with it for at least 1% of a month. Failure to do so will cause the address to be revoked after 3 months. And for B and A classes. If the networks do not route and cannot be accessed through their gateway, the block grant should be revoked and NAT or VPN should be used instead. This should give us a few more years until we come up with a radical replacement of the current internet. Not that IPv6 crap..