I'm not the guy you replied to, but come on. Install some big software like MATLAB or MS Office, oh no there goes several GB for each one. Set up a few VMs, oops there goes tens more GBs. Install some modern video games, multiple GB each one. And that's without even getting to the obvious culprits of pictures, music, and video.
64 GB would only work for a computer used almost exclusively for doing things on remote systems (browsing internet, working on remote servers, storing things on external HDs, etc).
VM's, mostly. Compilers, secondary. Blender, Inkscape. And then there's the big builds I do: the Linux kernel, rootfs, MOAI .. this all adds up and is quite space-filling.
If all I was doing is produce Word .docs and a few spreadsheets, I'm sure it'd be fine. But if you're a modern developer in the F/OSS world, 128gigs is barely enough to get rolling ..
64 GB would only work for a computer used almost exclusively for doing things on remote systems (browsing internet, working on remote servers, storing things on external HDs, etc).