In less formal and shorter communications, such as e-mail, this less often the case. On web pages, this style typically holds. However, the nature of the medium still dictates that these forms of organization are adapted. Perhaps Marshall McLuhan was at least partially right when he said, the medium is the message. I will discuss adornment shortly.
Delivery involves the medium quality, effectiveness, and appropriateness.
Categorization involves the nature of our cognition. How do we perceive, remember and recall information. This should influence what is important for the speaker and audience.