The wonderful series of articles ("Beward of Income-Tax Casuistry") on the income tax in the August, September, and October issues of Freedom Daily by Sheldon Richman is not online yet, but it is worth getting a copy of the three issues from the Future of Freedom Foundation. Among other things, Richman shows that the federal government can tax incomes without the 16th amendment. He proves that "Congress always had the power to tax anything." Richman also concludes: "Like it or not, the U.S. Constitution empowers the Congress to levy any tax it wants. You may read the Constitution otherwise, but the constitutionally endowed courts have spoken."
So, even if the FairTax did abolish the 16th amendment (which it doesn't), we could still end up with an income tax and a national sales tax. Another important point of Richman's article is that the income tax cannot be ignored by most Americans because it only applies to incomes derived from some federal privilege.