The fair tax system seems to benefit the top 1% the most, who are generally the people who are most skilled at moving their money around and bribing border officials to let them pass their foreign-bought goods into the country without having to pay taxes on it. 

If you don't think that'd happen, you're hopelessly naive.

And that's to say nothing of the very large number of businesses that would under-report the amount of business they do so that they could keep some of that tax money for themselves. 

If you don't think that'd happen, either, you're hopelessly naive.

Between these two situations, we'd end up with large amounts of money falling out of the country or being handed around privately, with absolutely no ability on the part of the government to trace it or collect their share.  Tax evasion would become so rampant that the government would collapse due to a lack of income.  And it's not like people in other countries would be spending their money on U.S. goods and services, either, due to the exorbitant tax rates.

The fair tax concept reminds me of many other thoroughly, almost childishly naive libertarian princples, that run on the assumption that all people are basically good and honest..... which, biologically speaking, we aren't.