In fairness, what we have right now is 48-bit addressing, not 64-bit. I've already run into cases of programs figuring that a "64-bit" address space is basical

In fairness, what we have right now is 48-bit addressing, not 64-bit. I've already run into cases of programs figuring that a "64-bit" address space is basically infinite and running out of address space by trying to have tens to hundreds of thousands of 4GB memory mappings (not necessarily backed by RAM).