Quoting RFC2860 [Re: I-D Action:draft-azinger-scalable-addressing-00.txt]

[Tony Li]

Hi Bill,

> 	is there an unstated assumption that all networks that use IPv6 addressing 
> 	WILL interconnect with each other?  


No, but there is an unstated assumption that the routing and addressing architecture is for the Internet. 

Certainly if someone is running a v6 network that is not Internet connected, then they are welcome to do whatever they like.  ;-)

Tony