DeLong argues that the beneficiaries of trade – both of the conventional goods for goods trade and the new goods for IOUs trade – are diffuse, and often don’t even realize how much they are benefiting from various forms of trade.  DeLong (in Martin Wolf’s forum via Mark Thoma): 

In the United States, at least, the problem is that most beneficiaries from globalization don't really know that they are beneficiaries, or how much they benefit. Feckless congressmen and congresswomen don't understand that the American economy is cushioned from their fiscal policy stupidities by the ability of the U.S.government to sell bonds internationally on a jaw-droppingly unbelievable scale. Home sellers in California don't realize that they got such a good price because of financing from across the Pacific. Walmart shoppers see the "made in China" stickers, but don't understand what a good deal they are getting because the rulers of the PRC are desperate to sell the products that their workers make at always low prices in order to stay as close as possible to full employment.

DeLong is making the classic political economy argument – the winners from trade are diffuse and unorganized, and the losers are concentrated and organized.   Hence, there ends up being less trade than there should be.  

I only half agree.