I don't believe there is a 'rfc1918' in v6 (yet), I agree that it doesn't seem relevant, damaging perhaps though :)
So you how would interpret the combination of RFC4913 and the statistical analysis known as "the birthday problem"? I offer the interpretation of this as use of address space in a limited context that has a likelihood of collision at the prefix level with some other similar, but unrelated, use. I would characterize a more exact equivalent of RFC 1918 space in an IPv6 context as use of address space in a limited context that has a certainty of collision at the prefix level with some other similar, but unrelated, use.
It would appear that we are already well advanced down a path of reproducing many of the aspects of IPv4 address architecture in IPv6, to the point of producing analogies of RFC1918 private address space. It also seems to me that this entire thread is constructed upon a somewhat dubious initial premise, but then again that's not exactly uncommon is it? :-)
Geoff
