it's the tragedy of the americas, a few hudred years of colonialism, and it goes on.
To understand concerns in the ARIN region, I'd recommend that folks read the actual policy text and staff assessment at <https://www.arin.net/policy/proposals/2009_3.html
. Because this global policy results in significant departure from RFC2050 need-based allocation (with one equal allocation unit per RIR each 6 month period even if less than regional demand), there are challenges of equity that result from mandating the return to the IANA.
The reality is that returned address space has been going back to IANA and will continue to do under current practices; see <http://blog.icann.org/2008/02/recovering-ipv4-address-space/
for more information.
Thanks! /John John Curran President and CEO ARIN