All the communication technologies we use — telephones, newspapers, radio, IM, e-mail, mailing lists, TV, books — are mired in historical cruft that keeps us from seeing clearly what to build next. It is useful to go to first principles, then reexamine whatever communication task you have at hand. So let me suggest the following basic dimensions of communication:
Timing: instantaneous (IM, phone, TV), delayed (e-mail, TV) or slow (books, movies)?
Audience: one person (phone call), two (conference call, chat), a dozen, two hundred (mailing list) or everyone in the world (Website, Weblog)?
Mode: text, voice, video, audio, 3D — some mix of the above?
Length: short (IM) or long (movie, book)?
Persistence: evanescent (IM), temporary but retrievable (e-mail), published (Website, book) or pretty permanent (stone stele)?
Production Level: casual (ASCII e-mail), formal (proposal) or polished (movie, book)?
Identity: how much of your identity do you want to reveal? which identity (work, private)?
Permission: who can see or use the material?