It’s a famous phrase coined by McLuhan. He means that the form of a medium determines the kind of overall message it delivers. A case of scrolls carries a different message from a bound codex collecting those same scrolls, and so on. Whatever the hypothetical ability to deliver the same messages over books, TV, silent films, talkies, YouTube shorts, tweets, radio, handwritten letters, emails, et c., in practice the media themselves shape the messages that they deliver, so the broader “message” they effect in the form of shaping society and public life are very different.
I'm not sure how that affects the arguments at play here. Social media is not a single thing. It has various forms each bearing its own kind of "message" revealing and influencing parts of society in a variety of ways depending on the platform.
It's a lot easier to not have to delineate the myriad of effects that each platform has on its users and issue broad-sweeping legislation that will have consequences on how information is distributed and how people can interact with each other according to how information is spread.
We're dealing with technology capable of containing various kinds of media at a scale far unlike what McLuhan observed 60 years ago. That's not so say that he's become obsolete.
Read this and let me know if I'm getting it wrong...
https://web.archive.org/web/20060605204535/http://individual...