Trade Creation vs. Trade Diversion

In the NY Times, Daniel Altman looks at some economic concerns raised by the new US - South Korea free trade agreement.
The economic issue: are these bilateral trade agreements (i.e. deals between just two countries) trade creating or trade diverting? If the reduction of barriers with South Korea leads us to import a good from them, rather than from a third country which is actually the low-cost producer (but doesn't have a trade deal with us), economic efficiency is actually decreased.
The political economy issue: does the increasing focus on bilateral and regional agreements reduce the effort devoted to the big multilateral deals like the Doha round of the GATT/WTO negotiations?

UPDATE: This issue is the subject of discussion in the FT's "Economists Forum," which has a panel of economists discussing Martin Wolf's columns (the column itself is subscription-only, but the discussion is free).