A recent article in the Economist discussing which is the "best" language stays on my mind. The author's observation that "Tariana, from Brazil, has "evidentiality": speakers choose one of five verb-endings to show how they know what they aver to be true" makes me wonder if this might be a most useful linguistic characteristic in an era of truthiness.
A bit more (and only a bit more) research reveals that: "[i]n Tariana, an Arawak language spoken in the multilingual area of the Vaupe´s in northwest Amazonia,speakers have to specify whether they saw the event happen, or heard it, or know about it because somebody else told them, etc."
Yes, this would be most useful.
Missouri State of Mind 