Seems a bit questionable to me to allocate the IPv6 equivalent of class As when we haven't the slightest idea how things will evolve and we have experience in blowing through an "inconceivably large address space".
The IPv6 equivalent of a class A address block is a /8. We are not talking about allocating /8s to anyone, we are mainly talking about allocating /24s which are the equivalent of IPv4 class C blocks. This is one area where the IPv4 arithmetic and IPv6 arithemetic match up nicely. If you are worried about using up all the addresses, an IPv6 /24 and an IPv4 /24 use up the same percentage of the total address space. The very fact that we are discussing allocations in the region of /19 to /24 demonstrates the success of IPv6 in expanding the size of the address space. In IPv4, a really big ISP would get a /8. In IPv6 we can handle a really big ISP with one /13 and a medium sized ISP can fit into a /32, which in IPv4 can only handle a single host. When discussing the risk of runout, you have to look at actual numbers and actual percentages of the total number space. I suggest examining some of Geoff Huston's work in more detail. --Michael Dillon