On the Monday Message Board, Gianna asks “Are blogs chatrooms”, and observes:
my view is that perhaps blogs with comment facilities could be seen as chatrooms, though it puts the blogger more in the role of moderator than writer, i guess. but blogs without comment facilities are a bit of a stretch.
A closely related question came up on Tim Lambert’s blog, in reference to the increasingly-ludicrous John Lott, who refers to USENet discussion groups (arguably, the predecessors of blogs) as “Internet chat rooms”.
Obviously a blog isn’t a chatroom, and the presence of a comments facility doesn’t make it so. Political blogs like this one are intended as competition for mass media such as newspapers opinion-oriented magazines like Quadrant or The New Republic and the Op-Ed pages of newspapers, and have had at least some success in this role. If adding a comments facility to an online newspaper Op-Ed page makes a chatroom, then the New York Times is a chatroom.
What then, makes a chatroom a chatroom? To answer this, it’s best to go back to the original, Internet Relay Chat, which provided the most basic version. The distinguishing feature of IRC was that it provided a screen which refreshed automatically when ever anyone who was logged in typed something (more precisely, when they hit the “Return” key). This gives rise to the “room” metaphor – everyone “in the room” (that is, logged in) can “hear” everything said there. The subsequent developments of chatrooms (lists of who’s in the room, avatars, “getting a room” and so on) all follow from this.
Although I’m confident in the correctness of the above analysis, I should say that my total time spent in chatrooms would not amount to more than about three hours over the last fifteen years. I find them unutterably boring. I can see that they would provide an excellent venue for anonymous assignations, but attempting any discussion is like trying to hold a seminar in a crowded discotheque.
UpdateKen Parish picks me up on the sloppy statement in the original that blogs compete with newspapers. As he says (and as I’ve said in the past) blogs have a symbiotic/parasitic relationship with the news media. I’ve edited the post accordingly.
John Quiggin 
No wonder you’re feeling lonely John. No sooner have you come up with a new topic, and the head armadillo has already grabbed it and is off down the road with it lickety split …
yeah, on that definition of chatroom I completely agree, John–nothing like a blog. i suppose i was thinking of it more abstractly, that in a sense having a website where you say something and then other people come along and say something could conceivably be construed as being a ‘chatroom’. (i’ve only ever been in a chatroom of the type you describe once or twice too, since every time i said something i was comprehensively ignored by people apparently talking some weird teenage code…)
I don’t understand, Chris. What is this “new topic” concept?
Yeah they are different