Well, Twitter, Facebook, etc. are the modern replacements for the "status updates" you used to put in your .plan file. .plan was just a simple text file you left in your home directory; it would be displayed to any user who attempted to query you with the 'finger' command. These days the 'finger' protocol is not really used anymore due to security vulnerabilities. But back then, Unix really was a social-moedia OS, and the internet was a decentralized, federated social network.

(There were actually two such files; .project was used to give a high-level summary of what you were working on, while .plan was used to talk in detail about what you were currently doing at the moment.)