lanc writes "Bill Joy, co-founder of Sun, contributor to BSD Unix, the UltraSparc technology, NFS and even Java, tells the story in an article at TheRegister about how he wrote vi and what the motives were. In the interview he says:
"It was really hard to do because you've got to remember that I was trying to make it usable over a 300 baud modem. That's also the reason you have all these funny commands. It just barely worked to use a screen editor over a modem. It was just barely fast enough. A 1200 baud modem was an upgrade. 1200 baud now is pretty slow."
...and so my son begun The Holy Editor War."