[Andy from Beaverton]

Fair tax is a fair idea.

[xcamel]

Fair tax is still a really bad idea.

[GSlob]

"Fair"? It is a double taxation fraud, pure and simple. Say, you have 2 otherwise identical people, one with X (say, $100K - the number does not matter) in a 401k, and another with the same $100K, but in a Roth or in a regular savings account.
Both start withdrawing and spending their money under "fair tax" system. The former would be paying consumption tax, but that would be instead of the previously deferred income tax he has not paid to get his 401k. The double taxation issue concerns the latter: he will be hit with the consumption tax on top of the income taxes he has already paid to put that same 100K into his Roth or in the saving account.
Thus, unless there are specific compensatory provisions, like up-indexing of all after-tax accounts, it is a double taxation fraud.