...we could communicate via smell?

Sight, Sound, Taste, Touch, Smell. Five senses and many modes of communication. The first modes that are usually thought of when communication is considered are most likely involve sound; verbal-auditory communication. Language has evolved so that one person making a unique patter of sounds and syllables can be easily understood by another person. It is very possible that this form of communication, however, was preceded by more visual forms of communication like sign language (light is faster than sound after all).

The next step in the evolution of communication was perhaps visual. Man learned to transcribe his verbal language onto stone, papyrus, and other more permanent forms. In addition to allowing verbal communication to take a physical form, transcribed information is also the basis for non-linguistic means of communication like mathematics. Braille also transform touch into an equally powerful mode of communicaiton. 

Beyond these very distinct forms of communication that allow us to transmit very specific feelings or thoughts, music and graphic art also serve as a means of conveying a broade range of emotions. But what of taste and smell? What is it about these senses that limits our ability to communicate intellegently with them?

One might argue that chefs communicate via the flavors they concoct or that scented candles can communicate as well, but how much information can truly be conveyed? If one says that something is good or bad, or if one sees "good" or "bad" written down on a piece of paper, one immediately processes the information and connects it to a particular feeling. Similarly, in music, if one hears a major versus a minor chord, specific emotions may be evoked. There is a language that is associated with these concepts that can be passed easily from one person to another.

Is the potential for a means of communication via taste there? Perhaps it just has not been invented yet!