A friend once told me he bought a system with a 100MB hard drive because that was bigger than all his neighbors' drives.

The 640k RAM one similarly reminded me of when someone donated an old TRS-80 Model 12 to my high school, and they turned around and gave it to me. ("Well, we can either store it somewhere for a few years until we finally sell it at an auction for 50 cents... or we can ask Dave if he wants it.") In addition to being my first *nix system (Xenix, to be exact), it also included my first-ever hard drive, holding a whopping 12M. At the time, I was absolutely convinced that it would be all the disk space I would ever need for the rest of my life...