Here is one take on a blogging tetrad:
Blogging enhances “many to many” communication. As a medium, blogging allows me to get my message out to many without the need of access to television, radio, print or film production facilities. Blogging also allows me to receive messages from many sources.
Blogging obsolesces one to one or many to one communications. Telephone chats and television binges are replaced by blogging connections.
Blogging retrieves the habits of 18th letter correspondents or diarists. Though this varies widely, at the minimum blogging requires that we capture and express our thoughts via the keyboard. Some bloggers go much further than that.
When pushed to an extreme, blogging reverses into total narcissism. I write only to myself, for myself. I put myself into the blogosphere, and seeing my own image, become entranced.
I’m sure there are many other ways McLuhan would have analyzed blogging using his tetrad tool.