Except that Twitter allows and fosters interaction and participation, which makes it, at least in that regard, cool. I think the categories McLuhan used are to

Except that Twitter allows and fosters interaction and participation, which makes it, at least in that regard, cool. I think the categories McLuhan used are too limited to describe the media we have now. They conflate user participation with information density and with intensity of attention. Just too many things to represent with 'hot' or 'cool'.