I think we're in violent agreement. The only reason I included Firefox in the list is that I've seen it top 4GB on my own system. Maybe it's a x86-64 related memory leak, since all the memory measurements I hear people touting for the 32-bit version are far lower. Or maybe it's just full of pointers, which wouldn't be too surprising, really.
again, most people posting on the x32 subject don't even know what exactly is a mmap mapping, a shared memory segment, memory allocated from sbrk and other methods, stacks allocated dynamically, and jump to the conclusion a browser must require over 4GB of address space
Well I only included Firefox because, on my computer right now, it has mapped over 3GB, and has 2.1GB resident. That still fits within the 3GB/1GB split of 32-bit Linux. I have seen it go as high as 6GB, but its usual steady state for me is around 4GB. I never close any tabs. You're right though that a web-browser shouldn't require that much RAM under normal circumstances. FWIW, I am quite familiar with mmap, shared memory, sbrk, huge pages (including using mmap to map files on a hugetlbfs to get larger pages and improve my TLB performace), etc. I didn't include Firefox out of ignorance.
So, I reiterate: I think we're in violent agreement that x32 looks interesting and relevant, and the vast majority of applications don't need 64-bit, and many would benefit from smaller pointers.
A few applications I've written (large heuristic solvers, for example) benefit from 10GB - 15GB RAM. And from what I hear, some EDA apps they use at work could use 200+GB. And, of course, there's the ever present large databases, as you mentioned. But that's pretty specialized as compared to everything else.