At least, this will be big movement of IP assignment and hosting service provider. I think ARIN need to give some kind of introductory period for this policy, and need to apply some kind of loose procedure for this. Something like this. Apply 2 virtual hosting to 1 IP address for 6 month, and apply 4 virtual hosting to 1 IP address. In this case, hosting provider will have some room for applying virtual hosting based name-based web hosting, and they will have some time for testing new environment.
Nobody can change Internet environment suddenly.
At least we need some time to adjust this new concept to real world. Basically I agree with basic idea of this new policy. Just I don't like the way ARIN enforce this to ISP or real world.