Words delivered as electronic text are a great equalizer, for both the writer and the reader. Words impose no accessibility barriers for people with sensory disabilities. Words require minimal bandwidth. Even for readers with no significant disability or bandwidth limitation, words are great because the reader can read them in whatever way he or she sees fit (computer screen, e-ink display, printed page, text-to-speech).
Written words allow a writer to communicate without being hindered or prejudged by things beyond his or her control, such as accent, rate of speech, sound of voice, or poor acoustics. A writer can rewrite and edit his or her words to say exactly what he or she wants, far more easily than one can edit a video or audio recording.
Electronic text is more amenable to analysis and manipulation (e.g. translation) by machine than any other human communication medium.
I'm not so sure about this, but written words might favor reason over emotion, especially if one can disable presentation hints.
For these reasons and more, the Web should be primarily about written words delivered as electronic text.