Three Toed Sloth has a nice exposition on the difficulties of optimizing an economy, including the best explanation of convex optimization ever:
If plan A calls for 10,000 diapers and 2,000 towels, and plan B calls for 2,000 diapers and 10,000 towels, we could do half of plan A and half of plan B, make 6,000 diapers and 6,000 towels, and not run up against the constraints.
I saw this on Crooked Timber, and I have to say, it's one of the best blog posts I've read in a long time. Not just the thoughtful application of complexity theory, but there's a whole load of interesting political (gasp!) stuff in there.