Twitter's nebulous nature lends to inherent value for many groups of people. It can be so many things to so many different people. If you want to narrow down the selling proposition, then declaring it a new mode of communication would fit the bill pretty well.
The only issue with using "new mode of communication" to try to convince someone to use a service is that a new way of communicating appeals to people who are on the edge, but won't appeal to a widespread audience who might say "I don't need a new mode of communication, my current ones are working just fine."
It is a good point that twitter is revolutionizing gatherings of large groups of people (like at tradeshows and conferences) - maybe that is the way that it will get widespread adoption. Twittering at ballgames or concerts with lots of consumers? It's a possibility.
Resistance to "new things" is always the signature of something interesting. (I don't need a "word processor", my type writer is just fine; or I don't need a "copying machine", the world runs on carbon copy; or the best -- we don't need a "telephone", the telegraph is far superior!).
There is power in the chaotic nature of Twitter. I believe that a higher level of organization is about to emerge soon from the bedrock of what it currently is.
