>    Owen> IPv6.  Collision is just icing on the cake.
> For *INTERNET* access, you are right.
these systems fall into one of two categories (I will explain below).
> Enterprise network of some kind.
any address space without regard to internet numbering.
one has two options... GUA and ULA.
In either case, IPv6 provides the advantages of avoiding RFC-1918 and NAT.
certainly impossible across a few mergers and acquisitions of any size.
>    to span many miles of tundra.
"Internal" is a matter of topology, not geography.
>   bits of the Enterprise are used as "backbone" for these systems.
>   not know about said device, people start asking whois.
>   to have it an Enterprise.
So why not use GUA? Policy allows you to use GUA for such purposes.
Filter these GUA routes at the border and filter the packets too, just in case.
you won't have external leaks.
split horizon, just use DNS views (easy with BIND, not sure about other tools).
pointing in the right direction for those zones.
>   stamp in a /56 or /60 (as appropriate) into each instance sold.
rather than configured by the administrator.
>   that $2500 once... but $1250 every year?
a link. Layer 2 addressing operates in a completely flat topology.
certain amount of topological information.
better and no worse than RFC-1918.
only your squat and not 5,000 other squatters using the same space.
>>> that is the problem.
>    Owen> addresses?
> Why do I see large ISPs with multiple ASs?
> Why isn't all their traffic local?  Why aren't their networks convex?
If they were entirely internal non-connected networks, you wouldn't. They are not. They are globally connected networks and their internal structures are exposed in order to facilitate better routing where they touch the internet.
> One hand does not know what the other hand is doing, and does not need to.
>    Owen> you who the addresses belong to?
> emphasis on "SHOULD"
suck just as bad as RFC-1918. If you don't want that suckage, use GUA.