Wal-Mart doe not run a centralized economy. It runs a business that buys items for one price in one location, then sells them at another price in another.

Running an economy is a political affair. People can decide not to go to Wal-Mart; they cannot as easily decide not to be a citizen.

Quite frankly, a large majority of the horrors of the 20th century were due to folks thinking "Oh, I understand where we went wrong this last time with our centralized planning. This time will be much better!" There's a ton of reasons for this -- enough to put in a book. Or several books. And those books are out there if you are interested in them.

A related question is this: can you run just a simple store like Wal-Mart through a technocracy? You probably can to a certain degree, then it falls apart. The more you can automate, of course, the less actual value you are creating. Software continues to eat the world.

But no, feedback cycle time is not the issue. Not even close.