(And why should you? If it's an even swap, your net asset position can't have changed in an accounting sense.)
Barter is, of course, inefficient and ponderous--more of a hobby than a means to build up a modern economy. Nonetheless, as taxes go up and velocity (presumably) stays low, I expect we'll see more of it.
This article available online at:
http://www.theatlantic.com/business/archive/2009/05/gains-from-trade/17494/
