I have been struggling while reading McLuhan's "Understanding Media" to get his distinction between hot and cold media. Broadly I understand him to mean that cool media require more engagement from the consumer while hot media have more impact but require less participation. Film he sees as hot because it provides a rich and detailed visual experience and TV he considers cool because it is less impactful and needs more input from the viewer to complete the experience.
It is really frustrating that McLuhan didn't survive to see the internet develop because it would have been fascinating to have his perspective on the way it has matured. but in his absense and in his terms, it seems me coolest of cool media.
This is why I think that attempts to make it hot by adding graphics, audio, flash etc. just don't work. Not only do they not work but they actually feel intrusive. We want the internet to be cool, we want to fill in the gaps, we want it to be participatory. The things that work, that generate the most energy and have persisted are e-mail, newsgroups, IM and blogs all of which require high levels of engagement from participants.
And we are participants not consumers - sites that forget this won't last long.