I wrote Finger and developed the supporting database to provide this
information in traditional human terms -- real names and places. Because
I preferred to talk face to face rather than through the computer or
telephone, I put in the feature that tells how long the terminal had been
idle, so that I could assess the likelihood that I would find them there
if I walked down the hall.
The program was an instant hit. Some people asked for the Plan file
feature so that they could explain their absence or how they could be
reached at odd times, so I added it. I found it interesting that this
feature evolved into a forum for social commentary and amusing
observations.
I wonder what the world would be like today if Unix-like systems had gone more mainstream. Maybe ISPs would include a Unix account on their servers where you could set up your .plan file and things like 'finger' and 'talk' and regular email would fill the space, in a completely distributed and open manner, that Facebook and other social networks currently do.
Back when I was a kid, I used to regularly use finger check Carmack's .plan to see what he was up to.[1] Having never given this much thought, if you asked me about the origins of social media, I would have talked about MySpace and Friendster. Now I'd probably begin with talk and finger.