Hotter even than--still--what got us out of the Great Depression.
Here's Paulo Sapienza and Luigi Zingales: "Anti-Trust America: A trust deficit is driving our economy down".
Bruce Yandle: "Lost Trust: The Real Cause of the Financial Meltdown".
Robert J. Shiller was one of the first on the recent bandwagon with his Wall Street Journal piece about a month ago, "Animal Spirits Depend on Trust".
(Trend-spotter David Brooks is on board, too: "An Economy of Faith and Trust".)
The bad news is that trust is hard to study. The good news is that economists have been looking at it for a while. Paul J. Zak is one of the leaders. His 2001 Economic Journal paper (with Stephen Knack), "Trust and Growth" is interesting and already well-cited. (Working paper version.) Here's an application by Oguzhan C. Dincer and Eric M. Uslaner to data on U.S. states,