The large telecoms and cable outfits have tons of unused IP space that could be CIDR blocked out, think of the class A 24.X.X.X for instance that used to be @Home and Rodgers, large portions are empty! AT&T moved @Home to 12.X.X.X and then subsequently provides managed space to cable outfits like Mediacomm etc.
Now Mediacomm has just finally got around to getting its own space, is AT&T offering to CIDR out their precious class A?
No of course not, like some of the others, they get allocations from ARIN and sit on them instead of consolidating. They have scads of CIDR blocks used by all sorts of companies out there. Heck ARIN should just re-map some of those AT&T direct to the customers, let them keep the 12.X.X.X A Space.
Back in the day, Mark Lottor did mapping of all live ping able IP's before firewalls were so common and NAT extremely rare. If he were to make a comparison with whomever does like mapping today to those legacy maps and IP allocations, it would be a fascinating graphic to show the transformations and if by carrier, show how greedily the Worldcom/UUNets Sprints and Baby Bells have asked for space, color to their identity and now look to see many time those scattered CIDR blocks are empty. Sprint, old UUNet and Baby Bell CIDR's if unused, should get back into the pool.
Where is Mark Lottor and these newer guys with the latest IPV4 utilization's mapped out for the comparison analysis.
Enough said.