Re: Through Internet2 we can support a small number of very large flows
Fair point, but when what we know today as the Internet was ARPANET, it was just an experimental research network, and they had no idea it would grow into anything like what it was. Commercial use was forbidden until the 90s. There was no reason for MIT not to take a whole class A, because what possible worry would there be to run out of an address space measured in the billions when there's a limit of only a few tens of thousands of entities that would ever connect to what it was when these allocations were made in the mid 80s?
No worry of this with Internet2, even if they were still using a 32 bit address space, because technologies it develops would be adopted piecemeal by the real Internet. It isn't as though we'll say on Jan. 1 201x, everyone in the world has to update all network related hardware and software because they're picking up and moving everything over to Internet2. So if you get an email telling you to do that, it is probably spam :)