Today's Wall Street Journal has a convincing editorial on the Fair Tax concept:

Link... [1]

The only arguments which I have heard against the concept is that it is very regressive and harmful to those at the lowest rungs of society's economic ladder but the referenced article discusses the idea of "pre-bate" to protect the neediest.

So what are the pragmatic, rather than the ideological, arguments against the concept of the "fair tax"?